CS-Notes/notes/MySQL.md

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* [<EFBFBD>洢<EFBFBD><EFBFBD><EFBFBD><EFBFBD>](#<23>洢<EFBFBD><E6B4A2><EFBFBD><EFBFBD>)
    * [1. InnoDB](#1-innodb)
    * [2. MyISAM](#2-myisam)
    * [3. InnoDB <20><> MyISAM <20>ıȽ<C4B1>](#3-innodb-<2D><>-myisam-<2D>ıȽ<C4B1>)
* [<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>](#<23><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>)
    * [1. <20><><EFBFBD><EFBFBD>](#1-<2D><><EFBFBD><EFBFBD>)
    * [2. <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD>](#2-<2D><><EFBFBD><EFBFBD><EFBFBD><EFBFBD>)
    * [3. <20>ַ<EFBFBD><D6B7><EFBFBD>](#3-<2D>ַ<EFBFBD><D6B7><EFBFBD>)
    * [4. ʱ<><CAB1><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>](#4-ʱ<><CAB1><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>)
* [<EFBFBD><EFBFBD><EFBFBD><EFBFBD>](#<23><><EFBFBD><EFBFBD>)
    * [1. <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>](#1-<2D><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>)
        * [1.1 B-Tree <20><><EFBFBD><EFBFBD>](#11-b-tree-<2D><><EFBFBD><EFBFBD>)
        * [1.2 <20><>ϣ<EFBFBD><CFA3><EFBFBD><EFBFBD>](#12-<2D><>ϣ<EFBFBD><CFA3><EFBFBD><EFBFBD>)
        * [1.3. <20>ռ<EFBFBD><D5BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݣ<EFBFBD>R-Tree<65><65>](#13-<2D>ռ<EFBFBD><D5BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>r-tree)
        * [1.4 ȫ<><C8AB><EFBFBD><EFBFBD><EFBFBD><EFBFBD>](#14-ȫ<><C8AB><EFBFBD><EFBFBD><EFBFBD><EFBFBD>)
    * [2. <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ŵ<EFBFBD>](#2-<2D><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ŵ<EFBFBD>)
    * [3. <20><><EFBFBD><EFBFBD><EFBFBD>Ż<EFBFBD>](#3-<2D><><EFBFBD><EFBFBD><EFBFBD>Ż<EFBFBD>)
        * [3.1 <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>](#31-<2D><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>)
        * [3.2 ǰ׺<C7B0><D7BA><EFBFBD><EFBFBD>](#32-ǰ׺<C7B0><D7BA><EFBFBD><EFBFBD>)
        * [3.3 <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>](#33-<2D><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>)
        * [3.4 <20><><EFBFBD><EFBFBD><EFBFBD>е<EFBFBD>˳<EFBFBD><CBB3>](#34-<2D><><EFBFBD><EFBFBD><EFBFBD>е<EFBFBD>˳<EFBFBD><CBB3>)
        * [3.5 <20>۴<EFBFBD><DBB4><EFBFBD><EFBFBD><EFBFBD>](#35-<2D>۴<EFBFBD><DBB4><EFBFBD><EFBFBD><EFBFBD>)
        * [3.6 <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>](#36-<2D><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>)
    * [4. B-Tree <20><> B+Tree ԭ<><D4AD>](#4-b-tree-<2D><>-b+tree-ԭ<><D4AD>)
        * [4. 1 B-Tree](#4-1-b-tree)
        * [4.2 B+Tree](#42-b+tree)
        * [4.3 <20><><EFBFBD><EFBFBD>˳<EFBFBD><CBB3><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ָ<EFBFBD><D6B8><EFBFBD><EFBFBD> B+Tree](#43-<2D><><EFBFBD><EFBFBD>˳<EFBFBD><CBB3><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ָ<EFBFBD><D6B8><EFBFBD><EFBFBD>-b+tree)
        * [4.4 Ϊʲôʹ<C3B4><CAB9> B-Tree <20><> B+Tree](#44-Ϊʲôʹ<C3B4><CAB9>-b-tree-<2D><>-b+tree)
* [<EFBFBD><EFBFBD>ѯ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ż<EFBFBD>](#<23><>ѯ<EFBFBD><D1AF><EFBFBD><EFBFBD><EFBFBD>Ż<EFBFBD>)
    * [1. Explain](#1-explain)
    * [2. <20><><EFBFBD>ٷ<EFBFBD><D9B7>ص<EFBFBD><D8B5><EFBFBD>](#2-<2D><><EFBFBD>ٷ<EFBFBD><D9B7>ص<EFBFBD><D8B5><EFBFBD>)
    * [3. <20><><EFBFBD>ٷ<EFBFBD><D9B7>ص<EFBFBD><D8B5><EFBFBD>](#3-<2D><><EFBFBD>ٷ<EFBFBD><D9B7>ص<EFBFBD><D8B5><EFBFBD>)
    * [4. <20><><EFBFBD>ִ<EFBFBD><D6B4><EFBFBD> DELETE <20><> INSERT <20><><EFBFBD><EFBFBD>](#4-<2D><><EFBFBD>ִ<EFBFBD><D6B4><EFBFBD>-delete-<2D><>-insert-<2D><><EFBFBD><EFBFBD>)
* [<EFBFBD>ֿ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֱ<EFBFBD>](#<23>ֿ<EFBFBD><D6BF><EFBFBD><EFBFBD>ֱ<EFBFBD>)
* [<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ת<EFBFBD>ƺ͹<EFBFBD><EFBFBD>ϻָ<EFBFBD>](#<23><><EFBFBD><EFBFBD>ת<EFBFBD>ƺ͹<C6BA><CDB9>ϻָ<CFBB>)
    * [1. <20><><EFBFBD><EFBFBD>ת<EFBFBD><D7AA>](#1-<2D><><EFBFBD><EFBFBD>ת<EFBFBD><D7AA>)
    * [2. <20><><EFBFBD>ϻָ<CFBB>](#2-<2D><><EFBFBD>ϻָ<CFBB>)
* [<EFBFBD>ο<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>](#<23>ο<EFBFBD><CEBF><EFBFBD><EFBFBD><EFBFBD>)
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# <20>洢<EFBFBD><E6B4A2><EFBFBD><EFBFBD>

## 1. InnoDB

InnoDB <20><> MySQL <20><>Ĭ<EFBFBD><C4AC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>棬ֻ<E6A3AC><D6BB><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ҫ InnoDB <20><>֧<EFBFBD>ֵ<EFBFBD><D6B5><EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><CAB1><EFBFBD>ſ<EFBFBD><C5BF><EFBFBD>ʹ<EFBFBD><CAB9><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>洢<EFBFBD><E6B4A2><EFBFBD>档

<EFBFBD><EFBFBD><EFBFBD><EFBFBD> MVCC <20><>֧<EFBFBD>ָ߲<D6B8><DFB2><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʵ<EFBFBD><CAB5><EFBFBD><EFBFBD><EFBFBD>ĸ<EFBFBD><C4B8><EFBFBD>׼<EFBFBD>ĸ<EFBFBD><C4B8>뼶<EFBFBD><EBBCB6><EFBFBD><EFBFBD>Ĭ<EFBFBD>ϼ<EFBFBD><CFBC><EFBFBD><EFBFBD>ǿ<EFBFBD><C7BF>ظ<EFBFBD><D8B8><EFBFBD><EFBFBD><EFBFBD>

<EFBFBD><EFBFBD><EFBFBD>ǻ<EFBFBD><EFBFBD>ھ۴<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ģ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>IJ<EFBFBD>ѯ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>кܸߵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

<EFBFBD>ڲ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>˺ܶ<EFBFBD><EFBFBD>Ż<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ӵ<EFBFBD><EFBFBD>̶<EFBFBD>ȡ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><EFBFBD><EFBFBD>õĿ<EFBFBD>Ԥ<EFBFBD><EFBFBD><EFBFBD>Զ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ܹ<EFBFBD><EFBFBD>Զ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڴ<EFBFBD><EFBFBD>д<EFBFBD><EFBFBD><EFBFBD> hash <20><><EFBFBD><EFBFBD><EFBFBD>Լ<EFBFBD><D4BC>ٶ<EFBFBD><D9B6><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ӧ<EFBFBD><D3A6>ϣ<EFBFBD><CFA3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Լ<EFBFBD><D4BC>ܹ<EFBFBD><DCB9><EFBFBD><EFBFBD>ٲ<EFBFBD><D9B2><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>IJ<EFBFBD><C4B2>뻺<EFBFBD><EBBBBA><EFBFBD><EFBFBD><EFBFBD>ȡ<EFBFBD>

ͨ<EFBFBD><EFBFBD>һЩ<EFBFBD><EFBFBD><EFBFBD>ƺ͹<EFBFBD><EFBFBD><EFBFBD>֧<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȱ<EFBFBD><EFBFBD>ݡ<EFBFBD>

## 2. MyISAM

MyISAM <20>ṩ<EFBFBD>˴<EFBFBD><CBB4><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ԣ<EFBFBD><D4A3><EFBFBD><EFBFBD><EFBFBD>ȫ<EFBFBD><C8AB><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ѹ<EFBFBD><D1B9><EFBFBD><EFBFBD><EFBFBD>ռ亯<D5BC><E4BAAF><EFBFBD><EFBFBD>GIS<49><53><EFBFBD>ȡ<EFBFBD><C8A1><EFBFBD> MyISAM <20><>֧<EFBFBD><D6A7><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>м<EFBFBD><D0BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ұ<EFBFBD><D2B1><EFBFBD><EFBFBD><EFBFBD><EFBFBD>޷<EFBFBD><DEB7><EFBFBD>ȫ<EFBFBD>ָ<EFBFBD><D6B8><EFBFBD>

ֻ<EFBFBD>ܶ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ű<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>С<EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Զ<EFBFBD>ִ<EFBFBD>м<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>޸<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ǻ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ָ<EFBFBD><EFBFBD>Լ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ָ<EFBFBD><EFBFBD><EFBFBD>ͬ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ܵ<EFBFBD><EFBFBD><EFBFBD>һЩ<EFBFBD><EFBFBD><EFBFBD>ݶ<EFBFBD>ʧ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>޸<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ƿdz<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ġ<EFBFBD>

<EFBFBD><EFBFBD><EFBFBD>԰<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>̬<EFBFBD><EFBFBD><EFBFBD>߾<EFBFBD>̬<EFBFBD><EFBFBD><EFBFBD>С<EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ָ<EFBFBD><EFBFBD><EFBFBD><EFBFBD> DELAY_KEY_WRITE ѡ<><EFBFBD><EEA3AC>ÿ<EFBFBD><C3BF><EFBFBD>޸<EFBFBD>ִ<EFBFBD><D6B4><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><CAB1><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>޸ĵ<DEB8><C4B5><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>д<EFBFBD><D0B4><EFBFBD><EFBFBD><EFBFBD>̣<EFBFBD><CCA3><EFBFBD><EFBFBD>ǻ<EFBFBD>д<EFBFBD><D0B4><EFBFBD>ڴ<EFBFBD><DAB4>еļ<D0B5><C4BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֻ<EFBFBD><D6BB><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>߹رձ<D8B1><D5B1><EFBFBD>ʱ<EFBFBD><CAB1><EFBFBD>ŻὫ<C5BB><E1BDAB>Ӧ<EFBFBD><D3A6><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>д<EFBFBD><D0B4><EFBFBD><EFBFBD><EFBFBD>̡<EFBFBD><CCA1><EFBFBD><EFBFBD>ַ<EFBFBD>ʽ<EFBFBD><CABD><EFBFBD>Լ<EFBFBD><D4BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>д<EFBFBD><D0B4><EFBFBD><EFBFBD><EFBFBD>ܣ<EFBFBD><DCA3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݿ<EFBFBD><DDBF><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><CAB1><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>𻵣<EFBFBD><F0BBB5A3><EFBFBD>Ҫִ<D2AA><D6B4><EFBFBD>޸<EFBFBD><DEB8><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڴ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ժ󣬲<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ٽ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>޸IJ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ı<EFBFBD><EFBFBD>ʺϲ<EFBFBD><EFBFBD><EFBFBD> MyISAM ѹ<><D1B9><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֻ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݣ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>߱<EFBFBD><EFBFBD>Ƚ<EFBFBD>С<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>޸<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ȼ<EFBFBD><EFBFBD><EFBFBD>Լ<EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD><EFBFBD> MyISAM<41><4D>

MyISAM <20><><EFBFBD>Ƽ򵥣<C6BC><F2B5A5A3><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Խ<EFBFBD><D4BD>ܸ<EFBFBD>ʽ<EFBFBD>洢<EFBFBD><E6B4A2><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ijЩ<C4B3><D0A9><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ܺܺá<DCBA>

## 3. InnoDB <20><> MyISAM <20>ıȽ<C4B1>

**<2A><><EFBFBD><EFBFBD>**

InnoDB <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>͵ġ<CDB5>

**<2A><><EFBFBD><EFBFBD>**

InnoDB ֧<><D6A7><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȱ<EFBFBD><C8B1>ݡ<EFBFBD>

**<2A><><EFBFBD><EFBFBD><EFBFBD>ָ<EFBFBD>**

MyISAM <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>𻵵ĸ<F0BBB5B5><C4B8>ʱ<EFBFBD> InnoDB <20>ߺܶ࣬<DCB6><E0A3AC><EFBFBD>һָ<D2BB><D6B8><EFBFBD><EFBFBD>ٶ<EFBFBD>Ҳ<EFBFBD><D2B2><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

**<2A><><EFBFBD><EFBFBD>**

MyISAM ֻ֧<D6BB>ֱ<EFBFBD><D6B1><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> InnoDB <20><>֧<EFBFBD><D6A7><EFBFBD>м<EFBFBD><D0BC><EFBFBD><EFBFBD><EFBFBD>

**<2A><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>**

MyISAM ֧<><D6A7>ȫ<EFBFBD><C8AB><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ռ<EFBFBD><D5BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

# <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

## 1. <20><><EFBFBD><EFBFBD>

TINYINT, SMALLINT, MEDIUMINT, INT, BIGINT <20>ֱ<EFBFBD>ʹ<EFBFBD><CAB9> 8, 16, 24, 64 λ<>洢<EFBFBD>ռ䣬һ<E4A3AC><D2BB><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ԽС<D4BD><D0A1><EFBFBD><EFBFBD>Խ<EFBFBD>á<EFBFBD>

INT(11) <20>е<EFBFBD><D0B5><EFBFBD><EFBFBD><EFBFBD>ֻ<EFBFBD>ǹ涨<C7B9>˽<EFBFBD><CBBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʾ<EFBFBD>ַ<EFBFBD><D6B7>ĸ<EFBFBD><C4B8><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڴ洢<DAB4>ͼ<EFBFBD><CDBC><EFBFBD><EFBFBD><EFBFBD>˵<EFBFBD><CBB5>û<EFBFBD><C3BB><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ġ<EFBFBD>

## 2. <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

FLOAT <20><> DOUBLE Ϊ<><CEAA><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͣ<EFBFBD>DECIMAL Ϊ<>߾<EFBFBD><DFBE><EFBFBD>С<EFBFBD><D0A1><EFBFBD><EFBFBD><EFBFBD>͡<EFBFBD>CPU ԭ<><D4AD>֧<EFBFBD>ָ<EFBFBD><D6B8><EFBFBD><EFBFBD><EFBFBD><EFBFBD>㣬<EFBFBD><E3A3AC><EFBFBD>Dz<EFBFBD>֧<EFBFBD><D6A7> DECIMAl <20><><EFBFBD>͵ļ<CDB5><C4BC>㣬<EFBFBD><E3A3AC><EFBFBD><EFBFBD> DECIMAL <20>ļ<EFBFBD><C4BC><EFBFBD><EFBFBD>ȸ<EFBFBD><C8B8><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ҫ<EFBFBD><D2AA><EFBFBD>ߵĴ<DFB5><C4B4>ۡ<EFBFBD>

FLOAT<EFBFBD><EFBFBD>DOUBLE <20><> DECIMAL <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ָ<EFBFBD><D6B8><EFBFBD>п<EFBFBD><D0BF><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> DECIMAL(18, 9) <20><>ʾ<EFBFBD>ܹ<EFBFBD> 18 λ<><CEBB>ȡ 9 λ<>洢С<E6B4A2><D0A1><EFBFBD><EFBFBD><EFBFBD>֣<EFBFBD>ʣ<EFBFBD><CAA3> 9 λ<>洢<EFBFBD><E6B4A2><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>֡<EFBFBD>

## 3. <20>ַ<EFBFBD><D6B7><EFBFBD>

<EFBFBD><EFBFBD>Ҫ<EFBFBD><EFBFBD> CHAR <20><> VARCHAR <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͣ<EFBFBD>һ<EFBFBD><D2BB><EFBFBD>Ƕ<EFBFBD><C7B6><EFBFBD><EFBFBD>ģ<EFBFBD>һ<EFBFBD><D2BB><EFBFBD>DZ䳤<C7B1>ġ<EFBFBD>

VARCHAR <20><><EFBFBD>ֱ䳤<D6B1><E4B3A4><EFBFBD><EFBFBD><EFBFBD>ܹ<EFBFBD><DCB9><EFBFBD>ʡ<EFBFBD>ռ䣬<D5BC><E4A3AC>Ϊֻ<CEAA><D6BB>Ҫ<EFBFBD>洢<EFBFBD><E6B4A2>Ҫ<EFBFBD><D2AA><EFBFBD><EFBFBD><EFBFBD>ݡ<EFBFBD><DDA1><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ִ<EFBFBD><D6B4> UPDATE ʱ<><CAB1><EFBFBD>ܻ<EFBFBD>ʹ<EFBFBD>б<EFBFBD><D0B1>ñ<EFBFBD>ԭ<EFBFBD><D4AD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><D2BB>ҳ<EFBFBD><D2B3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ɵĴ<C9B5>Сʱ<D0A1><CAB1><EFBFBD><EFBFBD>Ҫִ<D2AA>ж<EFBFBD><D0B6><EFBFBD><EFBFBD>IJ<EFBFBD><C4B2><EFBFBD><EFBFBD><EFBFBD>MyISAM <20>Ὣ<EFBFBD>в<EFBFBD><D0B2>ɲ<EFBFBD>ͬ<EFBFBD><CDAC>Ƭ<EFBFBD>δ洢<CEB4><E6B4A2><EFBFBD><EFBFBD> InnoDB <20><><EFBFBD><EFBFBD>Ҫ<EFBFBD><D2AA><EFBFBD><EFBFBD>ҳ<EFBFBD><D2B3>ʹ<EFBFBD>зŽ<D0B7>ҳ<EFBFBD>ڡ<EFBFBD>

VARCHAR <20>ᱣ<EFBFBD><E1B1A3><EFBFBD>ַ<EFBFBD><D6B7><EFBFBD>ĩβ<C4A9>Ŀո񣬶<D5B8> CHAR <20><>ɾ<EFBFBD><C9BE><EFBFBD><EFBFBD>

## 4. ʱ<><CAB1><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

MySQL <20>ṩ<EFBFBD><E1B9A9><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ƶ<EFBFBD><C6B5><EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><CAB1><EFBFBD><EFBFBD><EFBFBD>ͣ<EFBFBD>DATATIME <20><> TIMESTAMP<4D><50>

**DATATIME**

<EFBFBD>ܹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> 1001 <20>굽 9999 <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ں<EFBFBD>ʱ<EFBFBD>䣬<EFBFBD><E4A3AC><EFBFBD><EFBFBD>Ϊ<EFBFBD>룬ʹ<EBA3AC><CAB9> 8 <20>ֽڵĴ洢<C4B4>ռ䡣

<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><EFBFBD><EFBFBD>޹ء<EFBFBD>

Ĭ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>£<EFBFBD>MySQL <20><>һ<EFBFBD>ֿ<EFBFBD><D6BF><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ġ<EFBFBD><C4A1><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ĸ<EFBFBD>ʽ<EFBFBD><CABD>ʾ DATATIME ֵ<><D6B5><EFBFBD><EFBFBD><EFBFBD>硰2008-01016 22:37:08<30><38><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> ANSI <20><>׼<EFBFBD><D7BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ں<EFBFBD>ʱ<EFBFBD><CAB1><EFBFBD><EFBFBD>ʾ<EFBFBD><CABE><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

**TIMESTAMP**

<EFBFBD><EFBFBD> UNIX ʱ<><CAB1><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͬ<EFBFBD><CDAC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> 1970 <20><> 1 <20><> 1 <20><><EFBFBD><EFBFBD>ҹ<EFBFBD><D2B9><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD>䣩<EFBFBD><E4A3A9><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD><CAB9> 4 <20><><EFBFBD>ֽڣ<D6BD>ֻ<EFBFBD>ܱ<EFBFBD>ʾ<EFBFBD><CABE> 1970 <20><> <20><> 2038 <20>ꡣ

<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><EFBFBD><EFBFBD>йء<EFBFBD>

MySQL <20>ṩ<EFBFBD><E1B9A9> FROM_UNIXTIME() <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD> Unxi ʱ<><CAB1><EFBFBD><EFBFBD>ת<EFBFBD><D7AA>Ϊ<EFBFBD><CEAA><EFBFBD>ڣ<EFBFBD><DAA3><EFBFBD><EFBFBD>ṩ<EFBFBD><E1B9A9> UNIX_TIMESTAMP() <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ת<EFBFBD><D7AA>Ϊ Unix ʱ<><CAB1><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

Ĭ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>£<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʱû<EFBFBD><EFBFBD>ָ<EFBFBD><EFBFBD> TIMESTAMP <20>е<EFBFBD>ֵ<EFBFBD><D6B5><EFBFBD>Ὣ<EFBFBD><E1BDAB><EFBFBD><EFBFBD>ֵ<EFBFBD><D6B5><EFBFBD><EFBFBD>Ϊ<EFBFBD><CEAA>ǰʱ<C7B0>䡣

Ӧ<EFBFBD>þ<EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD><EFBFBD> TIMESTAMP<4D><50><EFBFBD><EFBFBD>Ϊ<EFBFBD><CEAA><EFBFBD><EFBFBD> DATETIME <20>ռ<EFBFBD>Ч<EFBFBD>ʸ<EFBFBD><CAB8>ߡ<EFBFBD>

# <20><><EFBFBD><EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڴ洢<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʵ<EFBFBD>ֵģ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڷ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʵ<EFBFBD>ֵģ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>Բ<EFBFBD>ͬ<EFBFBD>洢<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>в<EFBFBD>ͬ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͺ<EFBFBD>ʵ<EFBFBD>֡<EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ܹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>׽<EFBFBD><EFBFBD><EFBFBD>ѯ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

<EFBFBD><EFBFBD><EFBFBD>ڷdz<EFBFBD>С<EFBFBD>ı<EFBFBD><EFBFBD><EFBFBD><EFBFBD>󲿷<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>¼򵥵<EFBFBD>ȫ<EFBFBD><EFBFBD>ɨ<EFBFBD><EFBFBD><EFBFBD>Ƚ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ч<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>е<EFBFBD><EFBFBD><EFBFBD><EFBFBD>͵ı<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͷdz<EFBFBD><EFBFBD><EFBFBD>Ч<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ƕ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ش<EFBFBD><EFBFBD>͵ı<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ<EFBFBD><EFBFBD>۽<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>֮<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>£<EFBFBD><EFBFBD><EFBFBD>Ҫ<EFBFBD>õ<EFBFBD>һ<EFBFBD>ּ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֱ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֳ<EFBFBD><EFBFBD><EFBFBD>Ҫ<EFBFBD><EFBFBD>ѯ<EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݣ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>¼һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>¼<EFBFBD><EFBFBD>ƥ<EFBFBD>䣬<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD>÷<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

## 1. <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

### 1.1 B-Tree <20><><EFBFBD><EFBFBD>

B-Tree <20><><EFBFBD><EFBFBD><EFBFBD>Ǵ<EFBFBD><C7B4><EFBFBD><EFBFBD><EFBFBD> MySQL <20>洢<EFBFBD><E6B4A2><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĭ<EFBFBD><C4AC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>͡<EFBFBD>

<EFBFBD><EFBFBD>Ϊ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ҫ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȫ<EFBFBD><EFBFBD>ɨ<EFBFBD>裬ֻ<EFBFBD><EFBFBD>Ҫ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ɣ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>˲<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ٶȿ<EFBFBD><EFBFBD>ܶࡣ

<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ָ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ϊ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>У<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>й<EFBFBD>ͬ<EFBFBD><EFBFBD><EFBFBD>ɼ<EFBFBD><EFBFBD><EFBFBD>B-Tree <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȫ<EFBFBD><C8AB>ֵ<EFBFBD><D6B5><EFBFBD><EFBFBD>ֵ<EFBFBD><D6B5>Χ<EFBFBD>ͼ<EFBFBD>ǰ׺<C7B0><D7BA><EFBFBD>ң<EFBFBD><D2A3><EFBFBD><EFBFBD>м<EFBFBD>ǰ׺<C7B0><D7BA><EFBFBD><EFBFBD>ֻ<EFBFBD><D6BB><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ǰ׺<C7B0><D7BA><EFBFBD>ҡ<EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڲ<EFBFBD><EFBFBD>ң<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͷ<EFBFBD><EFBFBD>顣

<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ǰ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>е<EFBFBD>˳<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>в<EFBFBD><EFBFBD>ң<EFBFBD><EFBFBD><EFBFBD><EFBFBD>޷<EFBFBD>ʹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

### 1.2 <20><>ϣ<EFBFBD><CFA3><EFBFBD><EFBFBD>

<EFBFBD><EFBFBD><EFBFBD>ڹ<EFBFBD>ϣ<EFBFBD><EFBFBD>ʵ<EFBFBD>֣<EFBFBD><EFBFBD>ŵ<EFBFBD><EFBFBD>Dz<EFBFBD><EFBFBD>ҷdz<EFBFBD><EFBFBD>졣

<EFBFBD><EFBFBD> MySQL <20><>ֻ<EFBFBD><D6BB> Memory <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʽ֧<CABD>ֹ<EFBFBD>ϣ<EFBFBD><CFA3><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

InnoDB <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><D2BB><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĺ<EFBFBD><C4B9>ܽС<DCBD><D0A1><EFBFBD><EFBFBD><EFBFBD>Ӧ<EFBFBD><D3A6>ϣ<EFBFBD><CFA3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ij<EFBFBD><C4B3><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֵ<EFBFBD><D6B5>ʹ<EFBFBD>õķdz<C4B7>Ƶ<EFBFBD><C6B5>ʱ<EFBFBD><CAB1><EFBFBD><EFBFBD><EFBFBD><EFBFBD> B-Tree <20><><EFBFBD><EFBFBD>֮<EFBFBD><D6AE><EFBFBD>ٴ<EFBFBD><D9B4><EFBFBD>һ<EFBFBD><D2BB><EFBFBD><EFBFBD>ϣ<EFBFBD><CFA3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> B-Tree <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>й<EFBFBD>ϣ<EFBFBD><CFA3><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һЩ<D2BB>ŵ㣬<C5B5><E3A3AC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ٵĹ<D9B5>ϣ<EFBFBD><CFA3><EFBFBD>ҡ<EFBFBD>

<EFBFBD><EFBFBD><EFBFBD>ƣ<EFBFBD><EFBFBD><EFBFBD>ϣ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֻ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ϣֵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ָ<EFBFBD>룬<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>洢<EFBFBD>ֶ<EFBFBD>ֵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Բ<EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>е<EFBFBD>ֵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȡ<EFBFBD>С<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڴ<EFBFBD><EFBFBD>е<EFBFBD><EFBFBD>е<EFBFBD><EFBFBD>ٶȺܿ죬<EFBFBD><EFBFBD><EFBFBD>Դ󲿷<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ӱ<EFBFBD>첢<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ԣ<EFBFBD><EFBFBD>޷<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڷ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֻ֧<EFBFBD>־<EFBFBD>ȷ<EFBFBD><EFBFBD><EFBFBD>ң<EFBFBD><EFBFBD>޷<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڲ<EFBFBD><EFBFBD>ֲ<EFBFBD><EFBFBD>Һͷ<EFBFBD>Χ<EFBFBD><EFBFBD><EFBFBD>ң<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ϣ<EFBFBD><EFBFBD>ͻ<EFBFBD>ܶ࣬<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ٶȻ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ú<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

### 1.3. <20>ռ<EFBFBD><D5BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݣ<EFBFBD>R-Tree<65><65>

MyISAM <20>洢<EFBFBD><E6B4A2><EFBFBD><EFBFBD>֧<EFBFBD>ֿռ<D6BF><D5BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڵ<EFBFBD><DAB5><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݴ洢<DDB4><E6B4A2>

<EFBFBD>ռ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ά<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݣ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ч<EFBFBD><EFBFBD>ʹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ά<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ϲ<EFBFBD>ѯ<EFBFBD><EFBFBD>

### 1.4 ȫ<><C8AB><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

MyISAM <20>洢<EFBFBD><E6B4A2><EFBFBD><EFBFBD>֧<EFBFBD><D6A7>ȫ<EFBFBD><C8AB><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڲ<EFBFBD><DAB2><EFBFBD><EFBFBD>ı<EFBFBD><C4B1>еĹؼ<C4B9><D8BC>ʣ<EFBFBD><CAA3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֱ<EFBFBD>ӱȽ<D3B1><C8BD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>е<EFBFBD>ֵ<EFBFBD><D6B5>

ʹ<EFBFBD><EFBFBD> MATCH AGAINST<53><54><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͨ<EFBFBD><CDA8> WHERE<52><45>

## 2. <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ŵ<EFBFBD>

- <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>˷<EFBFBD><CBB7><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ҫɨ<D2AA><C9A8><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

- <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD><CDB4><EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><CAB1><EFBFBD><EFBFBD>

- <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD> I/O <20><>Ϊ˳<CEAA><CBB3> I/O<><4F>

## 3. <20><><EFBFBD><EFBFBD><EFBFBD>Ż<EFBFBD>

### 3.1 <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

<EFBFBD>ڽ<EFBFBD><EFBFBD>в<EFBFBD>ѯʱ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>в<EFBFBD><EFBFBD><EFBFBD><EFBFBD>DZ<EFBFBD><EFBFBD><EFBFBD>ʽ<EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD>֣<EFBFBD>Ҳ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ǻ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>IJ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>޷<EFBFBD>ʹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>IJ<EFBFBD>ѯ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD><EFBFBD> actor_id <20>е<EFBFBD><D0B5><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

```sql
SELECT actor_id FROM sakila.actor WHERE actor_id + 1 = 5;
```

### 3.2 ǰ׺<C7B0><D7BA><EFBFBD><EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD> BLOB<4F><42>TEXT <20><> VARCHAR <20><><EFBFBD>͵<EFBFBD><CDB5>У<EFBFBD><D0A3><EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD><CAB9>ǰ׺<C7B0><D7BA><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֻ<EFBFBD><D6BB><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʼ<EFBFBD>IJ<EFBFBD><C4B2><EFBFBD><EFBFBD>ַ<EFBFBD><D6B7><EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ǰ׺<EFBFBD><EFBFBD><EFBFBD>ȵ<EFBFBD>ѡȡ<EFBFBD><EFBFBD>Ҫ<EFBFBD><EFBFBD><EFBFBD><EFBFBD> **<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ѡ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>** <20><>ȷ<EFBFBD><C8B7><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ظ<EFBFBD><D8B8><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֵ<EFBFBD>ͼ<EFBFBD>¼<EFBFBD><C2BC><EFBFBD><EFBFBD><EFBFBD>ı<EFBFBD>ֵ<EFBFBD><D6B5>ѡ<EFBFBD><D1A1><EFBFBD><EFBFBD>Խ<EFBFBD>ߣ<EFBFBD><DFA3><EFBFBD>ѯЧ<D1AF><D0A7>ҲԽ<D2B2>ߡ<EFBFBD><DFA1><EFBFBD><EFBFBD><EFBFBD>ֵΪ 1 <20><><EFBFBD><EFBFBD>ʱÿ<CAB1><C3BF><EFBFBD><EFBFBD>¼<EFBFBD><C2BC><EFBFBD><EFBFBD>Ψһ<CEA8><D2BB><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ӧ<EFBFBD><D3A6>

### 3.3 <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ҫʹ<EFBFBD>ö<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ϊ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>в<EFBFBD>ѯʱ<EFBFBD><EFBFBD>ʹ<EFBFBD>ö<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD>ö<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ܸ<EFBFBD><EFBFBD>á<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>У<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ð<EFBFBD> actor_id <20><> file_id <20><><EFBFBD><EFBFBD>Ϊ<EFBFBD><CEAA><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

```sql
SELECT file_id, actor_ id FROM sakila.film_actor
WhERE actor_id = 1 OR film_id = 1;
```

### 3.4 <20><><EFBFBD><EFBFBD><EFBFBD>е<EFBFBD>˳<EFBFBD><CBB3>

<EFBFBD><EFBFBD>ѡ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ǿ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>з<EFBFBD><EFBFBD><EFBFBD>ǰ<EFBFBD>棬<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʾ<EFBFBD>Ľ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> customer_id <20><>ѡ<EFBFBD><D1A1><EFBFBD>Ա<EFBFBD> staff_id <20><><EFBFBD>ߣ<EFBFBD><DFA3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ð<EFBFBD> customer_id <20>з<EFBFBD><D0B7>ڶ<EFBFBD><DAB6><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ǰ<EFBFBD>档

```sql
SELECT COUNT(DISTINCT staff_id)/COUNT(*) AS staff_id_selectivity,
COUNT(DISTINCT customer_id)/COUNT(*) AS customer_id_selectivity,
COUNT(*)
FROM payment;
```

```html
   staff_id_selectivity: 0.0001
customer_id_selectivity: 0.0373
               COUNT(*): 16049
```

### 3.5 <20>۴<EFBFBD><DBB4><EFBFBD><EFBFBD><EFBFBD>

![](https://github.com/CyC2018/InterviewNotes/blob/master/pics/b9e9ae8c-e216-4c01-b267-a50dbeb98fa4.jpg)

<EFBFBD>۴<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͣ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݴ洢<EFBFBD><EFBFBD>ʽ<EFBFBD><EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD>۴ء<EFBFBD><EFBFBD><EFBFBD>ʾ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>к<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڵļ<EFBFBD>ֵ<EFBFBD><EFBFBD><EFBFBD>ܵش洢<EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>InnoDB <20>ľ۴<C4BE><DBB4><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>д<EFBFBD><D0B4><EFBFBD><EFBFBD><EFBFBD> B-Tree <20><>Ҷ<EFBFBD><D2B6>ҳ<EFBFBD>С<EFBFBD>

<EFBFBD><EFBFBD>Ϊ<EFBFBD>޷<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>д<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͬ<EFBFBD>ĵط<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֻ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD>۴<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

**<2A>ŵ<EFBFBD>**

1. <20><><EFBFBD>԰<EFBFBD><D4B0><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݱ<EFBFBD><DDB1><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD>𣬼<EFBFBD><F0A3ACBC><EFBFBD> I/O <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
2. <20><>Ϊ<EFBFBD><CEAA><EFBFBD>ݱ<EFBFBD><DDB1><EFBFBD><EFBFBD><EFBFBD> B-Tree <20>У<EFBFBD><D0A3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݷ<EFBFBD><DDB7>ʸ<EFBFBD><CAB8>졣

**ȱ<><C8B1>**

1. <20>۴<EFBFBD><DBB4><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>޶<EFBFBD><DEB6><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> I/O <20>ܼ<EFBFBD><DCBC><EFBFBD>Ӧ<EFBFBD>õ<EFBFBD><C3B5><EFBFBD><EFBFBD>ܣ<EFBFBD><DCA3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȫ<EFBFBD><C8AB><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڴ棬<DAB4><E6A3AC>û<EFBFBD><C3BB>Ҫ<EFBFBD>þ۴<C3BE><DBB4><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
2. <20><><EFBFBD><EFBFBD><EFBFBD>ٶ<EFBFBD><D9B6><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڲ<EFBFBD><DAB2><EFBFBD>˳<EFBFBD>򣬰<EFBFBD><F2A3ACB0><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>˳<EFBFBD><CBB3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ġ<EFBFBD>
3. <20><><EFBFBD>²<EFBFBD><C2B2><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ۺܸߣ<DCB8><DFA3><EFBFBD>Ϊÿ<CEAA><C3BF><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>µ<EFBFBD><C2B5>ж<EFBFBD><D0B6><EFBFBD><EFBFBD>ƶ<EFBFBD><C6B6><EFBFBD><EFBFBD>µ<EFBFBD>λ<EFBFBD>á<EFBFBD>
4. <20><><EFBFBD><EFBFBD><EFBFBD>뵽ij<EBB5BD><C4B3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ҳ<EFBFBD>У<EFBFBD><D0A3>洢<EFBFBD><E6B4A2><EFBFBD><EFBFBD><EFBFBD>Ὣ<EFBFBD><E1BDAB>ҳ<EFBFBD><D2B3><EFBFBD>ѳ<EFBFBD><D1B3><EFBFBD><EFBFBD><EFBFBD>ҳ<EFBFBD><D2B3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ɸ<EFBFBD><C9B8>У<EFBFBD>ҳ<EFBFBD><D2B3><EFBFBD>ѻᵼ<D1BB>±<EFBFBD>ռ<EFBFBD>ø<EFBFBD><C3B8><EFBFBD><EFBFBD>Ĵ<EFBFBD><C4B4>̿ռ䡣
5. <20><><EFBFBD><EFBFBD><EFBFBD>бȽ<D0B1>ϡ<EFBFBD>裬<EFBFBD><E8A3AC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ҳ<EFBFBD><D2B3><EFBFBD>ѵ<EFBFBD><D1B5><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݴ洢<DDB4><E6B4A2><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><CAB1><EFBFBD>۴<EFBFBD><DBB4><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ܵ<EFBFBD><DCB5><EFBFBD>ȫ<EFBFBD><C8AB>ɨ<EFBFBD><C9A8><EFBFBD>ٶȱ<D9B6><C8B1><EFBFBD><EFBFBD><EFBFBD>

### 3.6 <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ҫ<EFBFBD><EFBFBD>ѯ<EFBFBD><EFBFBD><EFBFBD>ֶε<EFBFBD>ֵ<EFBFBD><EFBFBD>

## 4. B-Tree <20><> B+Tree ԭ<><D4AD>

### 4. 1 B-Tree

![](https://github.com/CyC2018/InterviewNotes/blob/master/pics/5ed71283-a070-4b21-85ae-f2cbfd6ba6e1.jpg)

Ϊ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> B-Tree<65><65><EFBFBD><EFBFBD><EFBFBD>ȶ<EFBFBD><C8B6><EFBFBD>һ<EFBFBD><D2BB><EFBFBD><EFBFBD><EFBFBD>ݼ<EFBFBD>¼Ϊһ<CEAA><D2BB><EFBFBD><EFBFBD>Ԫ<EFBFBD><D4AA> [key, data]<5D><>key Ϊ<><CEAA>¼<EFBFBD>ļ<EFBFBD><C4BC><EFBFBD>data Ϊ<><CEAA><EFBFBD>ݼ<EFBFBD>¼<EFBFBD><C2BC> key <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݡ<EFBFBD>

B-Tree <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݽṹ<DDBD><E1B9B9>

- <20><><EFBFBD><EFBFBD>Ҷ<EFBFBD>ڵ<EFBFBD><DAB5><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͬ<EFBFBD><CDAC><EFBFBD><EFBFBD><EFBFBD>ȣ<EFBFBD>Ҳ<EFBFBD><D2B2><EFBFBD><EFBFBD>˵ B-Tree <20><>ƽ<EFBFBD><C6BD><EFBFBD>ģ<EFBFBD>
- һ<><D2BB><EFBFBD>ڵ<EFBFBD><DAB5>е<EFBFBD> key <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ҷǵݼ<C7B5><DDBC><EFBFBD><EFBFBD>У<EFBFBD>
- <20><><EFBFBD><EFBFBD>ij<EFBFBD><C4B3>ָ<EFBFBD><D6B8><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> key <20>ֱ<EFBFBD><D6B1><EFBFBD> key<sub>i</sub> <20><> key<sub>i+1</sub><EFBFBD><EFBFBD><EFBFBD>Ҳ<EFBFBD>Ϊ null<6C><6C><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ָ<EFBFBD><D6B8>ָ<EFBFBD><D6B8><EFBFBD>ڵ<EFBFBD><DAB5><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> key <20><><EFBFBD><EFBFBD> key<sub>i</sub> <20><>С<EFBFBD><D0A1> key<sub>i+1</sub><EFBFBD><EFBFBD>

<EFBFBD><EFBFBD> B-Tree <20>а<EFBFBD> key <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݵ<EFBFBD><DDB5>㷨<EFBFBD>dz<EFBFBD>ֱ<EFBFBD>ۣ<EFBFBD><DBA3><EFBFBD><EFBFBD>ȴӸ<C8B4><D3B8>ڵ<EFBFBD><DAB5><EFBFBD><EFBFBD>ж<EFBFBD><D0B6>ֲ<EFBFBD><D6B2>ң<EFBFBD><D2A3><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ҵ<EFBFBD><D2B5>򷵻ض<F2B7B5BB>Ӧ<EFBFBD>ڵ<EFBFBD><DAB5><EFBFBD> data<74><61><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ӧ<EFBFBD><D3A6><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ָ<EFBFBD><D6B8>ָ<EFBFBD><D6B8><EFBFBD>Ľڵ<C4BD><DAB5>ݹ<EFBFBD><DDB9><EFBFBD><EFBFBD>в<EFBFBD><D0B2>ң<EFBFBD>ֱ<EFBFBD><D6B1><EFBFBD>ҵ<EFBFBD><D2B5>ڵ<EFBFBD><DAB5><EFBFBD><EFBFBD>ҵ<EFBFBD> null ָ<>룬ǰ<EBA3AC>߲<EFBFBD><DFB2>ҳɹ<D2B3><C9B9><EFBFBD><EFBFBD><EFBFBD><EFBFBD>߲<EFBFBD><DFB2><EFBFBD>ʧ<EFBFBD>ܡ<EFBFBD>

<EFBFBD><EFBFBD><EFBFBD>ڲ<EFBFBD><EFBFBD><EFBFBD>ɾ<EFBFBD><EFBFBD><EFBFBD>µ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݼ<EFBFBD>¼<EFBFBD><EFBFBD><EFBFBD>ƻ<EFBFBD> B-Tree <20><><EFBFBD><EFBFBD><EFBFBD>ʣ<EFBFBD><CAA3><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ڲ<EFBFBD><DAB2><EFBFBD>ɾ<EFBFBD><C9BE>ʱ<EFBFBD><CAB1><EFBFBD><EFBFBD>Ҫ<EFBFBD><D2AA><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><D2BB><EFBFBD><EFBFBD><EFBFBD>ѡ<EFBFBD><D1A1>ϲ<EFBFBD><CFB2><EFBFBD>ת<EFBFBD>ƵȲ<C6B5><C8B2><EFBFBD><EFBFBD>Ա<EFBFBD><D4B1><EFBFBD> B-Tree <20><><EFBFBD>ʡ<EFBFBD>

### 4.2 B+Tree

![](https://github.com/CyC2018/InterviewNotes/blob/master/pics/63cd5b50-d6d8-4df6-8912-ef4a1dd5ba13.jpg)

<EFBFBD><EFBFBD> B-Tree <20><><EFBFBD>ȣ<EFBFBD>B+Tree <20><><EFBFBD><EFBFBD><EFBFBD>²<EFBFBD>ͬ<EFBFBD>㣺

- ÿ<><C3BF><EFBFBD>ڵ<EFBFBD><DAB5><EFBFBD>ָ<EFBFBD><D6B8><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ϊ 2d <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD> 2d+1<><31>
- <20>ڽڵ㲻<DAB5>洢 data<74><61>ֻ<EFBFBD>洢 key<65><79>Ҷ<EFBFBD>ӽڵ㲻<DAB5>洢ָ<E6B4A2>롣

### 4.3 <20><><EFBFBD><EFBFBD>˳<EFBFBD><CBB3><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ָ<EFBFBD><D6B8><EFBFBD><EFBFBD> B+Tree

![](https://github.com/CyC2018/InterviewNotes/blob/master/pics/1ee5f0a5-b8df-43b9-95ab-c516c54ec797.jpg)

һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݿ<EFBFBD>ϵͳ<EFBFBD><EFBFBD><EFBFBD>ļ<EFBFBD>ϵͳ<EFBFBD><EFBFBD>ʹ<EFBFBD>õ<EFBFBD> B+Tree <20>ṹ<EFBFBD><E1B9B9><EFBFBD>ھ<EFBFBD><DABE><EFBFBD> B+Tree <20><><EFBFBD><EFBFBD><EFBFBD>Ͻ<EFBFBD><CFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ż<EFBFBD><C5BB><EFBFBD><EFBFBD><EFBFBD>Ҷ<EFBFBD>ӽڵ<D3BD><DAB5><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>˳<EFBFBD><CBB3><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ָ<EFBFBD>룬<EFBFBD><EBA3AC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ż<EFBFBD><C5BB><EFBFBD>Ŀ<EFBFBD><C4BF><EFBFBD><EFBFBD>Ϊ<EFBFBD><CEAA><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʵ<EFBFBD><CAB5><EFBFBD><EFBFBD>ܡ<EFBFBD>

### 4.4 Ϊʲôʹ<C3B4><CAB9> B-Tree <20><> B+Tree

<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݽṹҲ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ļ<EFBFBD>ϵͳ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݿ<EFBFBD>ϵͳ<EFBFBD>ձ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> B-/+Tree <20><>Ϊ<EFBFBD><CEAA><EFBFBD><EFBFBD><EFBFBD>ṹ<EFBFBD><E1B9B9>

ҳ<EFBFBD>Ǽ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>洢<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>߼<EFBFBD><EFBFBD>飬Ӳ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ϵͳ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD><EFBFBD>̴洢<EFBFBD><EFBFBD><EFBFBD>ָ<EFBFBD>Ϊ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ĵ<EFBFBD>С<EFBFBD><EFBFBD><EFBFBD>ȵĿ飬ÿ<EFBFBD><EFBFBD><EFBFBD>洢<EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ϊһҳ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ϵͳ<EFBFBD>У<EFBFBD>ҳ<EFBFBD>ô<EFBFBD>Сͨ<EFBFBD><EFBFBD>Ϊ 4k<34><6B><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD><CDB4><EFBFBD><EFBFBD><EFBFBD>ҳΪ<D2B3><CEAA>λ<EFBFBD><CEBB><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݡ<EFBFBD>

һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>˵<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ҳ<EFBFBD>ܴ󣬲<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȫ<EFBFBD><EFBFBD><EFBFBD>洢<EFBFBD><EFBFBD><EFBFBD>ڴ<EFBFBD><EFBFBD>У<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ļ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʽ<EFBFBD>洢<EFBFBD>Ĵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ϡ<EFBFBD>Ϊ<EFBFBD>˼<EFBFBD><EFBFBD>ٴ<EFBFBD><EFBFBD><EFBFBD> I/O<><4F><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ϸ<EFBFBD><CFB8><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȡ<EFBFBD><C8A1><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ÿ<EFBFBD>ζ<EFBFBD><CEB6><EFBFBD>Ԥ<EFBFBD><D4A4><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ǽ<EFBFBD><C7BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ѧ<EFBFBD><D1A7><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ľֲ<C4BE><D6B2><EFBFBD>ԭ<EFBFBD><D4AD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><D2BB><EFBFBD><EFBFBD><EFBFBD>ݱ<EFBFBD><DDB1>õ<EFBFBD>ʱ<EFBFBD><CAB1><EFBFBD>丽<EFBFBD><E4B8BD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ҳͨ<D2B2><CDA8><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ϱ<EFBFBD>ʹ<EFBFBD>á<EFBFBD><C3A1><EFBFBD><EFBFBD>ݿ<EFBFBD>ϵͳ<CFB5><CDB3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>˴<EFBFBD><CBB4><EFBFBD>Ԥ<EFBFBD><D4A4>ԭ<EFBFBD><D4AD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><D2BB><EFBFBD>ڵ<EFBFBD><DAB5>Ĵ<EFBFBD>С<EFBFBD><D0A1>Ϊ<EFBFBD><CEAA><EFBFBD><EFBFBD>һ<EFBFBD><D2BB>ҳ<EFBFBD><D2B3><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ÿ<EFBFBD><C3BF><EFBFBD>ڵ<EFBFBD>ֻ<EFBFBD><D6BB>Ҫһ<D2AA><D2BB> I/O <20>Ϳ<EFBFBD><CDBF><EFBFBD><EFBFBD><EFBFBD>ȫ<EFBFBD><C8AB><EFBFBD>롣B-Tree <20><>һ<EFBFBD>μ<EFBFBD><CEBC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ҫ h-1 <20><> I/O<><4F><EFBFBD><EFBFBD><EFBFBD>ڵ㳣פ<E3B3A3>ڴ棩<DAB4><E6A3A9><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ӷ<EFBFBD>Ϊ O(h)=O(logdN)<29><>һ<EFBFBD><D2BB>ʵ<EFBFBD><CAB5>Ӧ<EFBFBD><D3A6><EFBFBD>У<EFBFBD><D0A3><EFBFBD><EFBFBD><EFBFBD> d <20>Ƿdz<C7B7><C7B3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>֣<EFBFBD>ͨ<EFBFBD><CDA8><EFBFBD><EFBFBD><EFBFBD><EFBFBD> 100<30><30><EFBFBD><EFBFBD><EFBFBD><EFBFBD> h <20>dz<EFBFBD>С<EFBFBD><D0A1>ͨ<EFBFBD><CDA8><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> 3<><33><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֽṹ<D6BD><E1B9B9>h <20><><EFBFBD><EFBFBD>Ҫ<EFBFBD><D2AA><EFBFBD>Ķࡣ<C4B6><E0A1A3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>߼<EFBFBD><DFBC>Ϻܽ<CFBA><DCBD>Ľڵ㣨<DAB5><E3A3A8><EFBFBD>ӣ<EFBFBD><D3A3><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ͽ<EFBFBD><CFBF>ܺ<EFBFBD>Զ<EFBFBD><D4B6><EFBFBD>޷<EFBFBD><DEB7><EFBFBD><EFBFBD>þֲ<C3BE><D6B2>ԣ<EFBFBD>Ч<EFBFBD><D0A7><EFBFBD><EFBFBD><EFBFBD>Ա<EFBFBD> B-Tree <20><><EFBFBD>ܶࡣ

B+Tree <20><><EFBFBD>ʺ<EFBFBD><CABA><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ԭ<EFBFBD><D4AD><EFBFBD><EFBFBD><EFBFBD>ڽڵ<DABD><DAB5><EFBFBD><EFBFBD><EFBFBD> d <20>йء<D0B9><D8A1><EFBFBD><EFBFBD><EFBFBD> B+Tree <20>ڽڵ<DABD>ȥ<EFBFBD><C8A5><EFBFBD><EFBFBD> data <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>˿<EFBFBD><CBBF><EFBFBD>ӵ<EFBFBD>и<EFBFBD><D0B8><EFBFBD><EFBFBD>ij<EFBFBD><C4B3>ȣ<EFBFBD>ӵ<EFBFBD>и<EFBFBD><D0B8>õ<EFBFBD><C3B5><EFBFBD><EFBFBD>ܡ<EFBFBD>

# <20><>ѯ<EFBFBD><D1AF><EFBFBD><EFBFBD><EFBFBD>Ż<EFBFBD>

## 1. Explain

<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> SQL <20><><EFBFBD>䣬<EFBFBD><E4A3AC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>бȽ<D0B1><C8BD><EFBFBD>Ҫ<EFBFBD><D2AA><EFBFBD>ֶ<EFBFBD><D6B6>У<EFBFBD>

- select_type : <20><>ѯ<EFBFBD><D1AF><EFBFBD>ͣ<EFBFBD><CDA3>м򵥲<D0BC>ѯ<EFBFBD><D1AF><EFBFBD><EFBFBD><EFBFBD>ϲ<EFBFBD>ѯ<EFBFBD><D1AF><EFBFBD>Ӳ<EFBFBD>ѯ

- key : ʹ<>õ<EFBFBD><C3B5><EFBFBD><EFBFBD><EFBFBD>

- rows : ɨ<><C9A8><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

## 2. <20><><EFBFBD>ٷ<EFBFBD><D9B7>ص<EFBFBD><D8B5><EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ѯ<EFBFBD><EFBFBD>Ҫ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ϊ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>˹<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݣ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>˷<EFBFBD><EFBFBD>ʹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>֮<EFBFBD>⣬Ҳ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>С<EFBFBD>

<EFBFBD><EFBFBD><EFBFBD>ò<EFBFBD>Ҫʹ<EFBFBD><EFBFBD> SELECT * <20><><EFBFBD>䣬Ҫ<E4A3AC><D2AA><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ҫѡ<D2AA><D1A1><EFBFBD><EFBFBD>ѯ<EFBFBD><D1AF><EFBFBD>С<EFBFBD>

## 3. <20><><EFBFBD>ٷ<EFBFBD><D9B7>ص<EFBFBD><D8B5><EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD><EFBFBD> LIMIT <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȡ<EFBFBD><C8A1><EFBFBD><EFBFBD>Ҫ<EFBFBD><D2AA><EFBFBD><EFBFBD>Щ<EFBFBD>С<EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Խ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȫ<EFBFBD><EFBFBD>ɨ<EFBFBD>衣<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>䣬<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ҫ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȫ<EFBFBD><EFBFBD>ɨ<EFBFBD>裬<EFBFBD><EFBFBD>ʹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֻ<EFBFBD><EFBFBD>Ҫɨ<EFBFBD>輸<EFBFBD>м<EFBFBD>¼<EFBFBD><EFBFBD><EFBFBD>ɣ<EFBFBD>ʹ<EFBFBD><EFBFBD> Explain <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͨ<EFBFBD><CDA8><EFBFBD>۲<EFBFBD> rows <20>ֶ<EFBFBD><D6B6><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֲ<EFBFBD><D6B2>졣

```sql
SELECT * FROM sakila.film_actor WHERE film_id = 1;
```

## 4. <20><><EFBFBD>ִ<EFBFBD><D6B4><EFBFBD> DELETE <20><> INSERT <20><><EFBFBD><EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ִ<EFBFBD>еĻ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ס<EFBFBD>ܶ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݡ<EFBFBD>ռ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>־<EFBFBD><EFBFBD><EFBFBD>ľ<EFBFBD>ϵͳ<EFBFBD><EFBFBD>Դ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ܶ<EFBFBD>С<EFBFBD>ĵ<EFBFBD><EFBFBD><EFBFBD>Ҫ<EFBFBD>IJ<EFBFBD>ѯ<EFBFBD><EFBFBD>

```sql
DELEFT FROM messages WHERE create < DATE_SUB(NOW(), INTERVAL 3 MONTH);
```
```sql
rows_affected = 0
do {
    rows_affected = do_query(
    "DELETE FROM messages WHERE create  < DATE_SUB(NOW(), INTERVAL 3 MONTH) LIMIT 10000")
} while rows_affected > 0
```

# <20>ֿ<EFBFBD><D6BF><EFBFBD><EFBFBD>ֱ<EFBFBD>

**1. <20>ֱ<EFBFBD><D6B1><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>IJ<EFBFBD>ͬ**

<EFBFBD>ֱ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ǽ<EFBFBD>һ<EFBFBD>ű<EFBFBD><EFBFBD>ֳɶ<EFBFBD><EFBFBD><EFBFBD>С<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ЩС<EFBFBD><EFBFBD>ӵ<EFBFBD>в<EFBFBD>ͬ<EFBFBD>ı<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ǽ<EFBFBD>һ<EFBFBD>ű<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݷ<EFBFBD>Ϊ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>飬<EFBFBD><EFBFBD>Щ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Դ洢<EFBFBD><EFBFBD>ͬһ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ϣ<EFBFBD>Ҳ<EFBFBD><EFBFBD><EFBFBD>Դ洢<EFBFBD>ڲ<EFBFBD>ͬ<EFBFBD>Ĵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ϣ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ַ<EFBFBD>ʽ<EFBFBD>±<EFBFBD><EFBFBD><EFBFBD>Ȼֻ<EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>

**2. ʹ<>÷ֿ<C3B7><D6BF><EFBFBD><EFBFBD>ֱ<EFBFBD><D6B1><EFBFBD>ԭ<EFBFBD><D4AD>**

<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ҵ<EFBFBD><EFBFBD><EFBFBD>ķ<EFBFBD>չ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݿ<EFBFBD><EFBFBD>еı<EFBFBD><EFBFBD><EFBFBD>Խ<EFBFBD><EFBFBD>Խ<EFBFBD>࣬<EFBFBD><EFBFBD><EFBFBD>ұ<EFBFBD><EFBFBD>е<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ҳ<EFBFBD><EFBFBD>Խ<EFBFBD><EFBFBD>Խ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD><EFBFBD>д<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ<EFBFBD><EFBFBD><EFBFBD>Ҳ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

**3. <20><>ֱ<EFBFBD>з<EFBFBD>**

<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ģ<EFBFBD>顢<EFBFBD><EFBFBD>ϵ<EFBFBD><EFBFBD><EFBFBD>г̶Ȼ<EFBFBD><EFBFBD>ֳ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>𵽲<EFBFBD>ͬ<EFBFBD>Ŀ<EFBFBD><EFBFBD>ϡ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>磬<EFBFBD><EFBFBD><EFBFBD>ǻὨ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ʒ<EFBFBD><EFBFBD><EFBFBD>ݿ<EFBFBD> payDB<44><42><EFBFBD>û<EFBFBD><C3BB><EFBFBD><EFBFBD>ݿ<EFBFBD> userDB <20>ȣ<EFBFBD><C8A3>ֱ<EFBFBD><D6B1><EFBFBD><EFBFBD><EFBFBD><EFBFBD>洢<EFBFBD><E6B4A2>Ŀ<EFBFBD><C4BF><EFBFBD><EFBFBD>Ʒ<EFBFBD>йصı<D8B5><C4B1><EFBFBD><EFBFBD><EFBFBD><EFBFBD>û<EFBFBD><C3BB>йصı<D8B5><C4B1><EFBFBD>

**4. ˮƽ<CBAE>з<EFBFBD>**

<EFBFBD>ѱ<EFBFBD><EFBFBD>е<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݰ<EFBFBD><EFBFBD><EFBFBD>ij<EFBFBD>ֹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>洢<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ṹ<EFBFBD><EFBFBD>ͬ<EFBFBD>ı<EFBFBD><EFBFBD>У<EFBFBD><EFBFBD><EFBFBD><EFBFBD>簴 id <20><>ɢ<EFBFBD><C9A2>ֵ<EFBFBD><D6B5><EFBFBD>Ա<EFBFBD><D4B1>Ƚ<EFBFBD><C8BD>л<EFBFBD><D0BB>֣<EFBFBD>

**5. <20><>ֱ<EFBFBD>з<EFBFBD><D0B7><EFBFBD>ˮƽ<CBAE>зֵ<D0B7>ѡ<EFBFBD><D1A1>**

<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݿ<EFBFBD><EFBFBD>еı<EFBFBD>̫<EFBFBD>࣬<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ҵ<EFBFBD><EFBFBD><EFBFBD>߼<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ô<EFBFBD><EFBFBD>ֱ<EFBFBD>з<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ѡ<EFBFBD><EFBFBD>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݿ<EFBFBD><EFBFBD>ı<EFBFBD><EFBFBD><EFBFBD><EFBFBD>࣬<EFBFBD><EFBFBD><EFBFBD>ǵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ܴ<EFBFBD><EFBFBD><EFBFBD>Ӧ<EFBFBD><EFBFBD>ѡ<EFBFBD><EFBFBD>ˮƽ<EFBFBD>з֡<EFBFBD>

**6. ˮƽ<CBAE>зֵ<D0B7>ʵ<EFBFBD>ַ<EFBFBD>ʽ**

<EFBFBD><EFBFBD><EFBFBD>򵥵<EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD><EFBFBD> merge <20>洢<EFBFBD><E6B4A2><EFBFBD>档

**7. <20>ֿ<EFBFBD><D6BF><EFBFBD><EFBFBD>ֱ<EFBFBD><D6B1><EFBFBD><EFBFBD>ڵ<EFBFBD><DAB5><EFBFBD><EFBFBD><EFBFBD>**

(1) <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

<EFBFBD><EFBFBD>ִ<EFBFBD>зֿ<EFBFBD><EFBFBD>ֱ<EFBFBD>֮<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݴ洢<EFBFBD><EFBFBD><EFBFBD>˲<EFBFBD>ͬ<EFBFBD>Ŀ<EFBFBD><EFBFBD>ϣ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݿ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ѡ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݿⱾ<EFBFBD><EFBFBD><EFBFBD>ķֲ<EFBFBD>ʽ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȥִ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>񣬽<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>߰<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ܴ<EFBFBD><EFBFBD>ۣ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ӧ<EFBFBD>ó<EFBFBD><EFBFBD><EFBFBD>ȥЭ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ƣ<EFBFBD><EFBFBD>γɳ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>߼<EFBFBD><EFBFBD>ϵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֻ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ɱ<EFBFBD><EFBFBD>̷<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ĸ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

(2) <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>

<EFBFBD><EFBFBD>ִ<EFBFBD><EFBFBD><EFBFBD>˷ֿ<EFBFBD><EFBFBD>ֱ<EFBFBD>֮<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ա<EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ὣԭ<EFBFBD><EFBFBD><EFBFBD>߼<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ժ<EFBFBD>ǿ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݻ<EFBFBD><EFBFBD>ֵ<EFBFBD><EFBFBD><EFBFBD>ͬ<EFBFBD>ı<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͬ<EFBFBD>Ŀ<EFBFBD><EFBFBD>ϡ<EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ӳ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ܵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ƣ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>޷<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>λ<EFBFBD>ڲ<EFBFBD>ͬ<EFBFBD>ֿ<EFBFBD><EFBFBD>ı<EFBFBD><EFBFBD><EFBFBD>Ҳ<EFBFBD>޷<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ӷֱ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ȳ<EFBFBD>ͬ<EFBFBD>ı<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ԭ<EFBFBD><EFBFBD>ֻ<EFBFBD><EFBFBD>Ҫһ<EFBFBD>β<EFBFBD>ѯ<EFBFBD><EFBFBD><EFBFBD>ܹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ɵ<EFBFBD>ҵ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ҫ<EFBFBD><EFBFBD><EFBFBD>ж<EFBFBD><EFBFBD>β<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ɡ<EFBFBD>

# <20><><EFBFBD><EFBFBD>ת<EFBFBD>ƺ͹<C6BA><CDB9>ϻָ<CFBB>

<EFBFBD><EFBFBD><EFBFBD><EFBFBD>ת<EFBFBD><EFBFBD>Ҳ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>л<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ֹ<EFBFBD><EFBFBD><EFBFBD>ʱ<EFBFBD><EFBFBD><EFBFBD>л<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>⣬ʹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ϊ<EFBFBD><EFBFBD><EFBFBD>⡣<EFBFBD><EFBFBD><EFBFBD>ϻָ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>˼<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ǵӹ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>лָ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ұ<EFBFBD>֤<EFBFBD><EFBFBD><EFBFBD>ݵ<EFBFBD><EFBFBD><EFBFBD>ȷ<EFBFBD>ԡ<EFBFBD>

## 1. <20><><EFBFBD><EFBFBD>ת<EFBFBD><D7AA>

**1.1 <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>л<EFBFBD><D0BB><EFBFBD>ɫ**

<EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ̨<EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ϊ<EFBFBD><EFBFBD><EFBFBD>⣬<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><EFBFBD><EFBFBD><EFBFBD>-<2D><><EFBFBD><EFBFBD><EFBFBD>ƽṹ<C6BD>е<EFBFBD><D0B5><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ͱ<EFBFBD><CDB1><EFBFBD><EFBFBD><EFBFBD>ɫ<EFBFBD><C9AB>

**1.2 <20><><EFBFBD><EFBFBD> IP <20><>ַ<EFBFBD><D6B7> IP <20>й<EFBFBD>**

Ϊ MySQL ʵ<><CAB5>ָ<EFBFBD><D6B8>һ<EFBFBD><D2BB><EFBFBD>߼<EFBFBD> IP <20><>ַ<EFBFBD><D6B7><EFBFBD><EFBFBD> MySQL ʵ<><CAB5>ʧЧʱ<D0A7><CAB1><EFBFBD><EFBFBD><EFBFBD>Խ<EFBFBD> IP <20><>ַת<D6B7>Ƶ<EFBFBD><C6B5><EFBFBD>һ̨ MySQL <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ϡ<EFBFBD>

**1.3 <20>м<EFBFBD><D0BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>**

ͨ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>·<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD>õķ<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ϡ<EFBFBD>

![](https://github.com/CyC2018/InterviewNotes/blob/master/pics/fabd5fa0-b75e-48d0-9e2c-31471945ceb9.jpg)

**1.4 <20><>Ӧ<EFBFBD><D3A6><EFBFBD>д<EFBFBD><D0B4><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ת<EFBFBD><D7AA>**

<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ת<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ϵ<EFBFBD>Ӧ<EFBFBD><EFBFBD><EFBFBD>п<EFBFBD><EFBFBD>ܵ<EFBFBD><EFBFBD><EFBFBD>Ӧ<EFBFBD>ñ<EFBFBD><EFBFBD><EFBFBD>̫<EFBFBD><EFBFBD><EFBFBD><EFBFBD>׾<EFBFBD><EFBFBD>

## 2. <20><><EFBFBD>ϻָ<CFBB>


# <20>ο<EFBFBD><CEBF><EFBFBD><EFBFBD><EFBFBD>

- <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD> MySQL
- [MySQL <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ݽṹ<DDBD><E1B9B9><EFBFBD>㷨ԭ<E3B7A8><D4AD> ](http://blog.codinglabs.org/articles/theory-of-mysql-index.html)
- [MySQL <20><><EFBFBD><EFBFBD><EFBFBD>Ż<EFBFBD>ȫ<EFBFBD><C8AB><EFBFBD><EFBFBD> ](http://www.runoob.com/w3cnote/mysql-index.html)
- [20+ <20><> MySQL <20><><EFBFBD><EFBFBD><EFBFBD>Ż<EFBFBD><C5BB><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ѿ<EFBFBD><D1BE><EFBFBD> ](https://www.jfox.info/20-tiao-mysql-xing-nen-you-hua-de-zui-jia-jing-yan.html)