auto commit
This commit is contained in:
CyC2018
parent
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@ -46,9 +46,22 @@ https://leetcode.com/problems/big-countries/description/
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+--------------+-------------+--------------+
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```
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## Solution
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```sql
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SELECT name,
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population,
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area
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FROM
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World
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WHERE
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area > 3000000
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OR population > 25000000;
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```
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## SQL Schema
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SQL Schema 用于在本地环境下创建表结构并导入数据，从而方便在本地环境解答。
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SQL Schema 用于在本地环境下创建表结构并导入数据，从而方便在本地环境调试。
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```sql
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DROP TABLE
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@ -64,19 +77,6 @@ VALUES
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( 'Angola', 'Africa', '1246700', '20609294', '1009900000' );
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```
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## Solution
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```sql
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SELECT name,
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population,
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area
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FROM
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World
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WHERE
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area > 3000000
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OR population > 25000000;
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```
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# 627. Swap Salary
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https://leetcode.com/problems/swap-salary/description/
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@ -103,6 +103,24 @@ https://leetcode.com/problems/swap-salary/description/
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| 4 | D | m | 500 |
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```
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## Solution
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两个相等的数异或的结果为 0，而 0 与任何一个数异或的结果为这个数。
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sex 字段只有两个取值：'f' 和 'm'，并且有以下规律：
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```
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'f' ^ ('m' ^ 'f') = 'm' ^ ('f' ^ 'f') = 'm'
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'm' ^ ('m' ^ 'f') = 'f' ^ ('m' ^ 'm') = 'f'
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```
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因此将 sex 字段和 'm' ^ 'f' 进行异或操作，最后就能反转 sex 字段。
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```sql
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UPDATE salary
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SET sex = CHAR ( ASCII(sex) ^ ASCII( 'm' ) ^ ASCII( 'f' ) );
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```
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## SQL Schema
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```sql
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@ -118,22 +136,6 @@ VALUES
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( '4', 'D', 'f', '500' );
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```
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## Solution
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使用异或操作，两个相等的数异或的结果为 0，而 0 与任何一个数异或的结果为这个数。
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```
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'f' ^ 'm' ^ 'f' = 'm'
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'm' ^ 'm' ^ 'f' = 'f'
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```
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```sql
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UPDATE salary
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SET sex = CHAR ( ASCII(sex) ^ ASCII( 'm' ) ^ ASCII( 'f' ) );
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```
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# 620. Not Boring Movies
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https://leetcode.com/problems/not-boring-movies/description/
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@ -164,6 +166,20 @@ https://leetcode.com/problems/not-boring-movies/description/
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+---------+-----------+--------------+-----------+
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```
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## Solution
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```sql
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SELECT
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*
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FROM
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cinema
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WHERE
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id % 2 = 1
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AND description != 'boring'
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ORDER BY
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rating DESC;
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```
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## SQL Schema
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```sql
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@ -180,20 +196,6 @@ VALUES
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( 5, 'House card', 'Interesting', 9.1 );
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```
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## Solution
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```sql
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SELECT
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*
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FROM
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cinema
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WHERE
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id % 2 = 1
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AND description != 'boring'
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ORDER BY
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rating DESC;
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```
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# 596. Classes More Than 5 Students
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https://leetcode.com/problems/classes-more-than-5-students/description/
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@ -226,6 +228,21 @@ https://leetcode.com/problems/classes-more-than-5-students/description/
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+---------+
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```
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## Solution
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对 class 列进行分组之后，再使用 count 汇总函数统计数量，统计之后使用 having 进行过滤。
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```sql
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SELECT
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class
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FROM
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courses
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GROUP BY
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class
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HAVING
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count( DISTINCT student ) >= 5;
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```
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## SQL Schema
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```sql
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@ -246,21 +263,6 @@ VALUES
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( 'I', 'Math' );
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```
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## Solution
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对 class 列进行分组之后，再使用 count 汇总函数统计数量，统计之后使用 having 进行过滤。
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```sql
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SELECT
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class
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FROM
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courses
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GROUP BY
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class
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HAVING
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count( DISTINCT student ) >= 5;
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```
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# 182. Duplicate Emails
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https://leetcode.com/problems/duplicate-emails/description/
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@ -289,20 +291,6 @@ https://leetcode.com/problems/duplicate-emails/description/
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+---------+
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```
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## SQL Schema
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```sql
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DROP TABLE
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IF
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EXISTS Person;
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CREATE TABLE Person ( Id INT, Email VARCHAR ( 255 ) );
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INSERT INTO Person ( Id, Email )
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VALUES
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( 1, 'a@b.com' ),
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( 2, 'c@d.com' ),
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( 3, 'a@b.com' );
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```
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## Solution
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对 Email 进行分组，如果相同 Email 的数量大于等于 2，则表示该 Email 重复。
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@ -318,6 +306,21 @@ HAVING
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COUNT( * ) >= 2;
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```
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## SQL Schema
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```sql
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DROP TABLE
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IF
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EXISTS Person;
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CREATE TABLE Person ( Id INT, Email VARCHAR ( 255 ) );
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INSERT INTO Person ( Id, Email )
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VALUES
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( 1, 'a@b.com' ),
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( 2, 'c@d.com' ),
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( 3, 'a@b.com' );
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```
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# 196. Delete Duplicate Emails
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https://leetcode.com/problems/delete-duplicate-emails/description/
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@ -347,10 +350,6 @@ https://leetcode.com/problems/delete-duplicate-emails/description/
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+----+------------------+
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```
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## SQL Schema
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与 182 相同。
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## Solution
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只保留相同 Email 中 Id 最小的那一个，然后删除其它的。
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@ -389,6 +388,12 @@ WHERE
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参考：[pMySQL Error 1093 - Can't specify target table for update in FROM clause](https://stackoverflow.com/questions/45494/mysql-error-1093-cant-specify-target-table-for-update-in-from-clause)
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## SQL Schema
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与 182 相同。
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# 175. Combine Two Tables
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https://leetcode.com/problems/combine-two-tables/description/
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@ -424,6 +429,22 @@ AddressId is the primary key column for this table.
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查找 FirstName, LastName, City, State 数据，而不管一个用户有没有填地址信息。
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## Solution
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涉及到 Person 和 Address 两个表，在对这两个表执行连接操作时，因为要保留 Person 表中的信息，即使在 Address 表中没有关联的信息也要保留。此时可以用左外连接，将 Person 表放在 LEFT JOIN 的左边。
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```sql
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SELECT
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FirstName,
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LastName,
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City,
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State
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FROM
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Person P
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LEFT JOIN Address A
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ON P.PersonId = A.PersonId;
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```
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## SQL Schema
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```sql
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@ -443,22 +464,6 @@ VALUES
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( 1, 2, 'New York City', 'New York' );
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```
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## Solution
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涉及到 Person 和 Address 两个表，在对这两个表执行连接操作时，因为要保留 Person 表中的信息，即使在 Address 表中没有关联的信息也要保留。此时可以用左外连接，将 Person 表放在 LEFT JOIN 的左边。
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```sql
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SELECT
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FirstName,
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LastName,
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City,
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State
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FROM
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Person P
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LEFT JOIN Address A
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ON P.PersonId = A.PersonId;
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```
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# 181. Employees Earning More Than Their Managers
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https://leetcode.com/problems/employees-earning-more-than-their-managers/description/
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@ -480,6 +485,18 @@ Employee 表：
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查找薪资大于其经理薪资的员工信息。
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## Solution
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```sql
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SELECT
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E1.NAME AS Employee
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FROM
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Employee E1
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INNER JOIN Employee E2
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ON E1.ManagerId = E2.Id
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AND E1.Salary > E2.Salary;
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```
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## SQL Schema
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```sql
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@ -495,18 +512,6 @@ VALUES
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( 4, 'Max', 90000, NULL );
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```
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## Solution
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```sql
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SELECT
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E1.NAME AS Employee
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FROM
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Employee E1
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INNER JOIN Employee E2
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ON E1.ManagerId = E2.Id
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AND E1.Salary > E2.Salary;
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```
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# 183. Customers Who Never Order
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https://leetcode.com/problems/customers-who-never-order/description/
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@ -548,29 +553,6 @@ Orders 表：
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+-----------+
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```
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## SQL Schema
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```sql
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DROP TABLE
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IF
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EXISTS Customers;
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CREATE TABLE Customers ( Id INT, NAME VARCHAR ( 255 ) );
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DROP TABLE
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IF
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EXISTS Orders;
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CREATE TABLE Orders ( Id INT, CustomerId INT );
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INSERT INTO Customers ( Id, NAME )
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VALUES
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( 1, 'Joe' ),
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( 2, 'Henry' ),
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( 3, 'Sam' ),
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( 4, 'Max' );
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INSERT INTO Orders ( Id, CustomerId )
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VALUES
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( 1, 3 ),
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( 2, 1 );
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```
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## Solution
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左外链接
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@ -597,6 +579,29 @@ WHERE
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Id NOT IN ( SELECT CustomerId FROM Orders );
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```
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## SQL Schema
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```sql
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DROP TABLE
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IF
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EXISTS Customers;
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CREATE TABLE Customers ( Id INT, NAME VARCHAR ( 255 ) );
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DROP TABLE
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IF
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EXISTS Orders;
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CREATE TABLE Orders ( Id INT, CustomerId INT );
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INSERT INTO Customers ( Id, NAME )
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VALUES
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( 1, 'Joe' ),
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( 2, 'Henry' ),
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( 3, 'Sam' ),
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( 4, 'Max' );
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INSERT INTO Orders ( Id, CustomerId )
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VALUES
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( 1, 3 ),
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( 2, 1 );
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```
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# 184. Department Highest Salary
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https://leetcode.com/problems/department-highest-salary/description/
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@ -638,25 +643,6 @@ Department 表：
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+------------+----------+--------+
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```
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## SQL Schema
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```sql
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DROP TABLE IF EXISTS Employee;
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CREATE TABLE Employee ( Id INT, NAME VARCHAR ( 255 ), Salary INT, DepartmentId INT );
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DROP TABLE IF EXISTS Department;
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CREATE TABLE Department ( Id INT, NAME VARCHAR ( 255 ) );
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INSERT INTO Employee ( Id, NAME, Salary, DepartmentId )
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VALUES
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( 1, 'Joe', 70000, 1 ),
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( 2, 'Henry', 80000, 2 ),
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( 3, 'Sam', 60000, 2 ),
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( 4, 'Max', 90000, 1 );
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INSERT INTO Department ( Id, NAME )
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VALUES
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( 1, 'IT' ),
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( 2, 'Sales' );
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```
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## Solution
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创建一个临时表，包含了部门员工的最大薪资。可以对部门进行分组，然后使用 MAX() 汇总函数取得最大薪资。
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@ -678,6 +664,26 @@ WHERE
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AND E.Salary = M.Salary;
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```
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## SQL Schema
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```sql
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DROP TABLE IF EXISTS Employee;
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CREATE TABLE Employee ( Id INT, NAME VARCHAR ( 255 ), Salary INT, DepartmentId INT );
|
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DROP TABLE IF EXISTS Department;
|
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CREATE TABLE Department ( Id INT, NAME VARCHAR ( 255 ) );
|
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INSERT INTO Employee ( Id, NAME, Salary, DepartmentId )
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VALUES
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( 1, 'Joe', 70000, 1 ),
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( 2, 'Henry', 80000, 2 ),
|
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( 3, 'Sam', 60000, 2 ),
|
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( 4, 'Max', 90000, 1 );
|
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INSERT INTO Department ( Id, NAME )
|
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VALUES
|
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( 1, 'IT' ),
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( 2, 'Sales' );
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```
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# 176. Second Highest Salary
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|
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https://leetcode.com/problems/second-highest-salary/description/
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|
|
@ -706,6 +712,15 @@ https://leetcode.com/problems/second-highest-salary/description/
|
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|
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没有找到返回 null 而不是不返回数据。
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## Solution
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为了在没有查找到数据时返回 null，需要在查询结果外面再套一层 SELECT。
|
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```sql
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SELECT
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( SELECT DISTINCT Salary FROM Employee ORDER BY Salary DESC LIMIT 1, 1 ) SecondHighestSalary;
|
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```
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|
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## SQL Schema
|
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|
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```sql
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|
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@ -720,25 +735,12 @@ VALUES
|
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( 3, 300 );
|
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```
|
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|
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## Solution
|
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|
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为了在没有查找到数据时返回 null，需要在查询结果外面再套一层 SELECT。
|
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|
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```sql
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SELECT
|
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( SELECT DISTINCT Salary FROM Employee ORDER BY Salary DESC LIMIT 1, 1 ) SecondHighestSalary;
|
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```
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# 177. Nth Highest Salary
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|
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## Description
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查找工资第 N 高的员工。
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## SQL Schema
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同 176。
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## Solution
|
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|
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```sql
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|
|
@ -750,6 +752,11 @@ RETURN ( SELECT ( SELECT DISTINCT Salary FROM Employee ORDER BY Salary DESC LIMI
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END
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```
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## SQL Schema
|
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|
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同 176。
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|
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# 178. Rank Scores
|
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|
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https://leetcode.com/problems/rank-scores/description/
|
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|
|
@ -786,23 +793,6 @@ https://leetcode.com/problems/rank-scores/description/
|
|||
+-------+------+
|
||||
```
|
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|
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## SQL Schema
|
||||
|
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```sql
|
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DROP TABLE
|
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IF
|
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EXISTS Scores;
|
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CREATE TABLE Scores ( Id INT, Score DECIMAL ( 3, 2 ) );
|
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INSERT INTO Scores ( Id, Score )
|
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VALUES
|
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( 1, 3.5 ),
|
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( 2, 3.65 ),
|
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( 3, 4.0 ),
|
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( 4, 3.85 ),
|
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( 5, 4.0 ),
|
||||
( 6, 3.65 );
|
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```
|
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|
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## Solution
|
||||
|
||||
要统计某个 score 的排名，只要统计大于该 score 的 score 数量，然后加 1。
|
||||
|
|
@ -852,6 +842,23 @@ ORDER BY
|
|||
S1.score DESC;
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
DROP TABLE
|
||||
IF
|
||||
EXISTS Scores;
|
||||
CREATE TABLE Scores ( Id INT, Score DECIMAL ( 3, 2 ) );
|
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INSERT INTO Scores ( Id, Score )
|
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VALUES
|
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( 1, 3.5 ),
|
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( 2, 3.65 ),
|
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( 3, 4.0 ),
|
||||
( 4, 3.85 ),
|
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( 5, 4.0 ),
|
||||
( 6, 3.65 );
|
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```
|
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|
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# 180. Consecutive Numbers
|
||||
|
||||
https://leetcode.com/problems/consecutive-numbers/description/
|
||||
|
|
@ -884,6 +891,21 @@ https://leetcode.com/problems/consecutive-numbers/description/
|
|||
+-----------------+
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
```sql
|
||||
SELECT
|
||||
DISTINCT L1.num ConsecutiveNums
|
||||
FROM
|
||||
Logs L1,
|
||||
Logs L2,
|
||||
Logs L3
|
||||
WHERE L1.id = l2.id - 1
|
||||
AND L2.id = L3.id - 1
|
||||
AND L1.num = L2.num
|
||||
AND l2.num = l3.num;
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
|
|
@ -902,21 +924,6 @@ VALUES
|
|||
( 7, 2 );
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
```sql
|
||||
SELECT
|
||||
DISTINCT L1.num ConsecutiveNums
|
||||
FROM
|
||||
Logs L1,
|
||||
Logs L2,
|
||||
Logs L3
|
||||
WHERE L1.id = l2.id - 1
|
||||
AND L2.id = L3.id - 1
|
||||
AND L1.num = L2.num
|
||||
AND l2.num = l3.num;
|
||||
```
|
||||
|
||||
# 626. Exchange Seats
|
||||
|
||||
https://leetcode.com/problems/exchange-seats/description/
|
||||
|
|
@ -951,22 +958,6 @@ seat 表存储着座位对应的学生。
|
|||
+---------+---------+
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
DROP TABLE
|
||||
IF
|
||||
EXISTS seat;
|
||||
CREATE TABLE seat ( id INT, student VARCHAR ( 255 ) );
|
||||
INSERT INTO seat ( id, student )
|
||||
VALUES
|
||||
( '1', 'Abbot' ),
|
||||
( '2', 'Doris' ),
|
||||
( '3', 'Emerson' ),
|
||||
( '4', 'Green' ),
|
||||
( '5', 'Jeames' );
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
使用多个 union。
|
||||
|
|
@ -1004,6 +995,22 @@ ORDER BY
|
|||
id;
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
DROP TABLE
|
||||
IF
|
||||
EXISTS seat;
|
||||
CREATE TABLE seat ( id INT, student VARCHAR ( 255 ) );
|
||||
INSERT INTO seat ( id, student )
|
||||
VALUES
|
||||
( '1', 'Abbot' ),
|
||||
( '2', 'Doris' ),
|
||||
( '3', 'Emerson' ),
|
||||
( '4', 'Green' ),
|
||||
( '5', 'Jeames' );
|
||||
```
|
||||
|
||||
|
||||
|
||||
|
||||
|
|
|
|||
|
|
@ -46,9 +46,22 @@ https://leetcode.com/problems/big-countries/description/
|
|||
+--------------+-------------+--------------+
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
```sql
|
||||
SELECT name,
|
||||
population,
|
||||
area
|
||||
FROM
|
||||
World
|
||||
WHERE
|
||||
area > 3000000
|
||||
OR population > 25000000;
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
SQL Schema 用于在本地环境下创建表结构并导入数据，从而方便在本地环境解答。
|
||||
SQL Schema 用于在本地环境下创建表结构并导入数据，从而方便在本地环境调试。
|
||||
|
||||
```sql
|
||||
DROP TABLE
|
||||
|
|
@ -64,19 +77,6 @@ VALUES
|
|||
( 'Angola', 'Africa', '1246700', '20609294', '1009900000' );
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
```sql
|
||||
SELECT name,
|
||||
population,
|
||||
area
|
||||
FROM
|
||||
World
|
||||
WHERE
|
||||
area > 3000000
|
||||
OR population > 25000000;
|
||||
```
|
||||
|
||||
# 627. Swap Salary
|
||||
|
||||
https://leetcode.com/problems/swap-salary/description/
|
||||
|
|
@ -103,6 +103,24 @@ https://leetcode.com/problems/swap-salary/description/
|
|||
| 4 | D | m | 500 |
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
两个相等的数异或的结果为 0，而 0 与任何一个数异或的结果为这个数。
|
||||
|
||||
sex 字段只有两个取值：'f' 和 'm'，并且有以下规律：
|
||||
|
||||
```
|
||||
'f' ^ ('m' ^ 'f') = 'm' ^ ('f' ^ 'f') = 'm'
|
||||
'm' ^ ('m' ^ 'f') = 'f' ^ ('m' ^ 'm') = 'f'
|
||||
```
|
||||
|
||||
因此将 sex 字段和 'm' ^ 'f' 进行异或操作，最后就能反转 sex 字段。
|
||||
|
||||
```sql
|
||||
UPDATE salary
|
||||
SET sex = CHAR ( ASCII(sex) ^ ASCII( 'm' ) ^ ASCII( 'f' ) );
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
|
|
@ -118,22 +136,6 @@ VALUES
|
|||
( '4', 'D', 'f', '500' );
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
使用异或操作，两个相等的数异或的结果为 0，而 0 与任何一个数异或的结果为这个数。
|
||||
|
||||
```
|
||||
'f' ^ 'm' ^ 'f' = 'm'
|
||||
'm' ^ 'm' ^ 'f' = 'f'
|
||||
```
|
||||
|
||||
|
||||
|
||||
```sql
|
||||
UPDATE salary
|
||||
SET sex = CHAR ( ASCII(sex) ^ ASCII( 'm' ) ^ ASCII( 'f' ) );
|
||||
```
|
||||
|
||||
# 620. Not Boring Movies
|
||||
|
||||
https://leetcode.com/problems/not-boring-movies/description/
|
||||
|
|
@ -164,6 +166,20 @@ https://leetcode.com/problems/not-boring-movies/description/
|
|||
+---------+-----------+--------------+-----------+
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
```sql
|
||||
SELECT
|
||||
*
|
||||
FROM
|
||||
cinema
|
||||
WHERE
|
||||
id % 2 = 1
|
||||
AND description != 'boring'
|
||||
ORDER BY
|
||||
rating DESC;
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
|
|
@ -180,20 +196,6 @@ VALUES
|
|||
( 5, 'House card', 'Interesting', 9.1 );
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
```sql
|
||||
SELECT
|
||||
*
|
||||
FROM
|
||||
cinema
|
||||
WHERE
|
||||
id % 2 = 1
|
||||
AND description != 'boring'
|
||||
ORDER BY
|
||||
rating DESC;
|
||||
```
|
||||
|
||||
# 596. Classes More Than 5 Students
|
||||
|
||||
https://leetcode.com/problems/classes-more-than-5-students/description/
|
||||
|
|
@ -226,6 +228,21 @@ https://leetcode.com/problems/classes-more-than-5-students/description/
|
|||
+---------+
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
对 class 列进行分组之后，再使用 count 汇总函数统计数量，统计之后使用 having 进行过滤。
|
||||
|
||||
```sql
|
||||
SELECT
|
||||
class
|
||||
FROM
|
||||
courses
|
||||
GROUP BY
|
||||
class
|
||||
HAVING
|
||||
count( DISTINCT student ) >= 5;
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
|
|
@ -246,21 +263,6 @@ VALUES
|
|||
( 'I', 'Math' );
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
对 class 列进行分组之后，再使用 count 汇总函数统计数量，统计之后使用 having 进行过滤。
|
||||
|
||||
```sql
|
||||
SELECT
|
||||
class
|
||||
FROM
|
||||
courses
|
||||
GROUP BY
|
||||
class
|
||||
HAVING
|
||||
count( DISTINCT student ) >= 5;
|
||||
```
|
||||
|
||||
# 182. Duplicate Emails
|
||||
|
||||
https://leetcode.com/problems/duplicate-emails/description/
|
||||
|
|
@ -289,20 +291,6 @@ https://leetcode.com/problems/duplicate-emails/description/
|
|||
+---------+
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
DROP TABLE
|
||||
IF
|
||||
EXISTS Person;
|
||||
CREATE TABLE Person ( Id INT, Email VARCHAR ( 255 ) );
|
||||
INSERT INTO Person ( Id, Email )
|
||||
VALUES
|
||||
( 1, 'a@b.com' ),
|
||||
( 2, 'c@d.com' ),
|
||||
( 3, 'a@b.com' );
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
对 Email 进行分组，如果相同 Email 的数量大于等于 2，则表示该 Email 重复。
|
||||
|
|
@ -318,6 +306,21 @@ HAVING
|
|||
COUNT( * ) >= 2;
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
DROP TABLE
|
||||
IF
|
||||
EXISTS Person;
|
||||
CREATE TABLE Person ( Id INT, Email VARCHAR ( 255 ) );
|
||||
INSERT INTO Person ( Id, Email )
|
||||
VALUES
|
||||
( 1, 'a@b.com' ),
|
||||
( 2, 'c@d.com' ),
|
||||
( 3, 'a@b.com' );
|
||||
```
|
||||
|
||||
|
||||
# 196. Delete Duplicate Emails
|
||||
|
||||
https://leetcode.com/problems/delete-duplicate-emails/description/
|
||||
|
|
@ -347,10 +350,6 @@ https://leetcode.com/problems/delete-duplicate-emails/description/
|
|||
+----+------------------+
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
与 182 相同。
|
||||
|
||||
## Solution
|
||||
|
||||
只保留相同 Email 中 Id 最小的那一个，然后删除其它的。
|
||||
|
|
@ -389,6 +388,12 @@ WHERE
|
|||
|
||||
参考：[pMySQL Error 1093 - Can't specify target table for update in FROM clause](https://stackoverflow.com/questions/45494/mysql-error-1093-cant-specify-target-table-for-update-in-from-clause)
|
||||
|
||||
## SQL Schema
|
||||
|
||||
与 182 相同。
|
||||
|
||||
|
||||
|
||||
# 175. Combine Two Tables
|
||||
|
||||
https://leetcode.com/problems/combine-two-tables/description/
|
||||
|
|
@ -424,6 +429,22 @@ AddressId is the primary key column for this table.
|
|||
|
||||
查找 FirstName, LastName, City, State 数据，而不管一个用户有没有填地址信息。
|
||||
|
||||
## Solution
|
||||
|
||||
涉及到 Person 和 Address 两个表，在对这两个表执行连接操作时，因为要保留 Person 表中的信息，即使在 Address 表中没有关联的信息也要保留。此时可以用左外连接，将 Person 表放在 LEFT JOIN 的左边。
|
||||
|
||||
```sql
|
||||
SELECT
|
||||
FirstName,
|
||||
LastName,
|
||||
City,
|
||||
State
|
||||
FROM
|
||||
Person P
|
||||
LEFT JOIN Address A
|
||||
ON P.PersonId = A.PersonId;
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
|
|
@ -443,22 +464,6 @@ VALUES
|
|||
( 1, 2, 'New York City', 'New York' );
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
涉及到 Person 和 Address 两个表，在对这两个表执行连接操作时，因为要保留 Person 表中的信息，即使在 Address 表中没有关联的信息也要保留。此时可以用左外连接，将 Person 表放在 LEFT JOIN 的左边。
|
||||
|
||||
```sql
|
||||
SELECT
|
||||
FirstName,
|
||||
LastName,
|
||||
City,
|
||||
State
|
||||
FROM
|
||||
Person P
|
||||
LEFT JOIN Address A
|
||||
ON P.PersonId = A.PersonId;
|
||||
```
|
||||
|
||||
# 181. Employees Earning More Than Their Managers
|
||||
|
||||
https://leetcode.com/problems/employees-earning-more-than-their-managers/description/
|
||||
|
|
@ -480,6 +485,18 @@ Employee 表：
|
|||
|
||||
查找薪资大于其经理薪资的员工信息。
|
||||
|
||||
## Solution
|
||||
|
||||
```sql
|
||||
SELECT
|
||||
E1.NAME AS Employee
|
||||
FROM
|
||||
Employee E1
|
||||
INNER JOIN Employee E2
|
||||
ON E1.ManagerId = E2.Id
|
||||
AND E1.Salary > E2.Salary;
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
|
|
@ -495,18 +512,6 @@ VALUES
|
|||
( 4, 'Max', 90000, NULL );
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
```sql
|
||||
SELECT
|
||||
E1.NAME AS Employee
|
||||
FROM
|
||||
Employee E1
|
||||
INNER JOIN Employee E2
|
||||
ON E1.ManagerId = E2.Id
|
||||
AND E1.Salary > E2.Salary;
|
||||
```
|
||||
|
||||
# 183. Customers Who Never Order
|
||||
|
||||
https://leetcode.com/problems/customers-who-never-order/description/
|
||||
|
|
@ -548,29 +553,6 @@ Orders 表：
|
|||
+-----------+
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
DROP TABLE
|
||||
IF
|
||||
EXISTS Customers;
|
||||
CREATE TABLE Customers ( Id INT, NAME VARCHAR ( 255 ) );
|
||||
DROP TABLE
|
||||
IF
|
||||
EXISTS Orders;
|
||||
CREATE TABLE Orders ( Id INT, CustomerId INT );
|
||||
INSERT INTO Customers ( Id, NAME )
|
||||
VALUES
|
||||
( 1, 'Joe' ),
|
||||
( 2, 'Henry' ),
|
||||
( 3, 'Sam' ),
|
||||
( 4, 'Max' );
|
||||
INSERT INTO Orders ( Id, CustomerId )
|
||||
VALUES
|
||||
( 1, 3 ),
|
||||
( 2, 1 );
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
左外链接
|
||||
|
|
@ -597,6 +579,29 @@ WHERE
|
|||
Id NOT IN ( SELECT CustomerId FROM Orders );
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
DROP TABLE
|
||||
IF
|
||||
EXISTS Customers;
|
||||
CREATE TABLE Customers ( Id INT, NAME VARCHAR ( 255 ) );
|
||||
DROP TABLE
|
||||
IF
|
||||
EXISTS Orders;
|
||||
CREATE TABLE Orders ( Id INT, CustomerId INT );
|
||||
INSERT INTO Customers ( Id, NAME )
|
||||
VALUES
|
||||
( 1, 'Joe' ),
|
||||
( 2, 'Henry' ),
|
||||
( 3, 'Sam' ),
|
||||
( 4, 'Max' );
|
||||
INSERT INTO Orders ( Id, CustomerId )
|
||||
VALUES
|
||||
( 1, 3 ),
|
||||
( 2, 1 );
|
||||
```
|
||||
|
||||
# 184. Department Highest Salary
|
||||
|
||||
https://leetcode.com/problems/department-highest-salary/description/
|
||||
|
|
@ -638,25 +643,6 @@ Department 表：
|
|||
+------------+----------+--------+
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
DROP TABLE IF EXISTS Employee;
|
||||
CREATE TABLE Employee ( Id INT, NAME VARCHAR ( 255 ), Salary INT, DepartmentId INT );
|
||||
DROP TABLE IF EXISTS Department;
|
||||
CREATE TABLE Department ( Id INT, NAME VARCHAR ( 255 ) );
|
||||
INSERT INTO Employee ( Id, NAME, Salary, DepartmentId )
|
||||
VALUES
|
||||
( 1, 'Joe', 70000, 1 ),
|
||||
( 2, 'Henry', 80000, 2 ),
|
||||
( 3, 'Sam', 60000, 2 ),
|
||||
( 4, 'Max', 90000, 1 );
|
||||
INSERT INTO Department ( Id, NAME )
|
||||
VALUES
|
||||
( 1, 'IT' ),
|
||||
( 2, 'Sales' );
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
创建一个临时表，包含了部门员工的最大薪资。可以对部门进行分组，然后使用 MAX() 汇总函数取得最大薪资。
|
||||
|
|
@ -678,6 +664,26 @@ WHERE
|
|||
AND E.Salary = M.Salary;
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
DROP TABLE IF EXISTS Employee;
|
||||
CREATE TABLE Employee ( Id INT, NAME VARCHAR ( 255 ), Salary INT, DepartmentId INT );
|
||||
DROP TABLE IF EXISTS Department;
|
||||
CREATE TABLE Department ( Id INT, NAME VARCHAR ( 255 ) );
|
||||
INSERT INTO Employee ( Id, NAME, Salary, DepartmentId )
|
||||
VALUES
|
||||
( 1, 'Joe', 70000, 1 ),
|
||||
( 2, 'Henry', 80000, 2 ),
|
||||
( 3, 'Sam', 60000, 2 ),
|
||||
( 4, 'Max', 90000, 1 );
|
||||
INSERT INTO Department ( Id, NAME )
|
||||
VALUES
|
||||
( 1, 'IT' ),
|
||||
( 2, 'Sales' );
|
||||
```
|
||||
|
||||
|
||||
# 176. Second Highest Salary
|
||||
|
||||
https://leetcode.com/problems/second-highest-salary/description/
|
||||
|
|
@ -706,6 +712,15 @@ https://leetcode.com/problems/second-highest-salary/description/
|
|||
|
||||
没有找到返回 null 而不是不返回数据。
|
||||
|
||||
## Solution
|
||||
|
||||
为了在没有查找到数据时返回 null，需要在查询结果外面再套一层 SELECT。
|
||||
|
||||
```sql
|
||||
SELECT
|
||||
( SELECT DISTINCT Salary FROM Employee ORDER BY Salary DESC LIMIT 1, 1 ) SecondHighestSalary;
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
|
|
@ -720,25 +735,12 @@ VALUES
|
|||
( 3, 300 );
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
为了在没有查找到数据时返回 null，需要在查询结果外面再套一层 SELECT。
|
||||
|
||||
```sql
|
||||
SELECT
|
||||
( SELECT DISTINCT Salary FROM Employee ORDER BY Salary DESC LIMIT 1, 1 ) SecondHighestSalary;
|
||||
```
|
||||
|
||||
# 177. Nth Highest Salary
|
||||
|
||||
## Description
|
||||
|
||||
查找工资第 N 高的员工。
|
||||
|
||||
## SQL Schema
|
||||
|
||||
同 176。
|
||||
|
||||
## Solution
|
||||
|
||||
```sql
|
||||
|
|
@ -750,6 +752,11 @@ RETURN ( SELECT ( SELECT DISTINCT Salary FROM Employee ORDER BY Salary DESC LIMI
|
|||
END
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
同 176。
|
||||
|
||||
|
||||
# 178. Rank Scores
|
||||
|
||||
https://leetcode.com/problems/rank-scores/description/
|
||||
|
|
@ -786,23 +793,6 @@ https://leetcode.com/problems/rank-scores/description/
|
|||
+-------+------+
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
DROP TABLE
|
||||
IF
|
||||
EXISTS Scores;
|
||||
CREATE TABLE Scores ( Id INT, Score DECIMAL ( 3, 2 ) );
|
||||
INSERT INTO Scores ( Id, Score )
|
||||
VALUES
|
||||
( 1, 3.5 ),
|
||||
( 2, 3.65 ),
|
||||
( 3, 4.0 ),
|
||||
( 4, 3.85 ),
|
||||
( 5, 4.0 ),
|
||||
( 6, 3.65 );
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
要统计某个 score 的排名，只要统计大于该 score 的 score 数量，然后加 1。
|
||||
|
|
@ -852,6 +842,23 @@ ORDER BY
|
|||
S1.score DESC;
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
DROP TABLE
|
||||
IF
|
||||
EXISTS Scores;
|
||||
CREATE TABLE Scores ( Id INT, Score DECIMAL ( 3, 2 ) );
|
||||
INSERT INTO Scores ( Id, Score )
|
||||
VALUES
|
||||
( 1, 3.5 ),
|
||||
( 2, 3.65 ),
|
||||
( 3, 4.0 ),
|
||||
( 4, 3.85 ),
|
||||
( 5, 4.0 ),
|
||||
( 6, 3.65 );
|
||||
```
|
||||
|
||||
# 180. Consecutive Numbers
|
||||
|
||||
https://leetcode.com/problems/consecutive-numbers/description/
|
||||
|
|
@ -884,6 +891,21 @@ https://leetcode.com/problems/consecutive-numbers/description/
|
|||
+-----------------+
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
```sql
|
||||
SELECT
|
||||
DISTINCT L1.num ConsecutiveNums
|
||||
FROM
|
||||
Logs L1,
|
||||
Logs L2,
|
||||
Logs L3
|
||||
WHERE L1.id = l2.id - 1
|
||||
AND L2.id = L3.id - 1
|
||||
AND L1.num = L2.num
|
||||
AND l2.num = l3.num;
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
|
|
@ -902,21 +924,6 @@ VALUES
|
|||
( 7, 2 );
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
```sql
|
||||
SELECT
|
||||
DISTINCT L1.num ConsecutiveNums
|
||||
FROM
|
||||
Logs L1,
|
||||
Logs L2,
|
||||
Logs L3
|
||||
WHERE L1.id = l2.id - 1
|
||||
AND L2.id = L3.id - 1
|
||||
AND L1.num = L2.num
|
||||
AND l2.num = l3.num;
|
||||
```
|
||||
|
||||
# 626. Exchange Seats
|
||||
|
||||
https://leetcode.com/problems/exchange-seats/description/
|
||||
|
|
@ -951,22 +958,6 @@ seat 表存储着座位对应的学生。
|
|||
+---------+---------+
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
DROP TABLE
|
||||
IF
|
||||
EXISTS seat;
|
||||
CREATE TABLE seat ( id INT, student VARCHAR ( 255 ) );
|
||||
INSERT INTO seat ( id, student )
|
||||
VALUES
|
||||
( '1', 'Abbot' ),
|
||||
( '2', 'Doris' ),
|
||||
( '3', 'Emerson' ),
|
||||
( '4', 'Green' ),
|
||||
( '5', 'Jeames' );
|
||||
```
|
||||
|
||||
## Solution
|
||||
|
||||
使用多个 union。
|
||||
|
|
@ -1004,6 +995,22 @@ ORDER BY
|
|||
id;
|
||||
```
|
||||
|
||||
## SQL Schema
|
||||
|
||||
```sql
|
||||
DROP TABLE
|
||||
IF
|
||||
EXISTS seat;
|
||||
CREATE TABLE seat ( id INT, student VARCHAR ( 255 ) );
|
||||
INSERT INTO seat ( id, student )
|
||||
VALUES
|
||||
( '1', 'Abbot' ),
|
||||
( '2', 'Doris' ),
|
||||
( '3', 'Emerson' ),
|
||||
( '4', 'Green' ),
|
||||
( '5', 'Jeames' );
|
||||
```
|
||||
|
||||
|
||||
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue
Block a user