From 44a57adc7e1c284c0eeb0bde000cf68e6dd04d96 Mon Sep 17 00:00:00 2001 From: CyC2018 Date: Wed, 28 Oct 2026 03:18:55 +0800 Subject: [PATCH] =?UTF-8?q?Update=20SQL=20=E7=BB=83=E4=B9=A0.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 调整代码块语言，补充参考资料。 --- notes/SQL 练习.md | 70 +++++++++++++++++++++++++---------------------- 1 file changed, 38 insertions(+), 32 deletions(-) diff --git a/notes/SQL 练习.md b/notes/SQL 练习.md index 3c3dc190..464a8cfd 100644 --- a/notes/SQL 练习.md +++ b/notes/SQL 练习.md @@ -16,6 +16,7 @@ * [178. Rank Scores](#178-rank-scores) * [180. Consecutive Numbers](#180-consecutive-numbers) * [626. Exchange Seats](#626-exchange-seats) + * [参考资料](#参考资料) @@ -25,7 +26,7 @@ https://leetcode.com/problems/big-countries/description/ ### Description -```html +```text +-----------------+------------+------------+--------------+---------------+ | name | continent | area | population | gdp | +-----------------+------------+------------+--------------+---------------+ @@ -39,7 +40,7 @@ https://leetcode.com/problems/big-countries/description/ 查找面积超过 3,000,000 或者人口数超过 25,000,000 的国家。 -```html +```text +--------------+-------------+--------------+ | name | population | area | +--------------+-------------+--------------+ @@ -85,7 +86,7 @@ https://leetcode.com/problems/swap-salary/description/ ### Description -```html +```text | id | name | sex | salary | |----|------|-----|--------| | 1 | A | m | 2500 | @@ -96,7 +97,7 @@ https://leetcode.com/problems/swap-salary/description/ 只用一个 SQL 查询，将 sex 字段反转。 -```html +```text | id | name | sex | salary | |----|------|-----|--------| | 1 | A | f | 2500 | @@ -145,7 +146,7 @@ https://leetcode.com/problems/not-boring-movies/description/ ### Description -```html +```text +---------+-----------+--------------+-----------+ | id | movie | description | rating | +---------+-----------+--------------+-----------+ @@ -159,7 +160,7 @@ https://leetcode.com/problems/not-boring-movies/description/ 查找 id 为奇数，并且 description 不是 boring 的电影，按 rating 降序。 -```html +```text +---------+-----------+--------------+-----------+ | id | movie | description | rating | +---------+-----------+--------------+-----------+ @@ -204,7 +205,7 @@ https://leetcode.com/problems/classes-more-than-5-students/description/ ### Description -```html +```text +---------+------------+ | student | class | +---------+------------+ @@ -222,7 +223,7 @@ https://leetcode.com/problems/classes-more-than-5-students/description/ 查找有五名及以上 student 的 class。 -```html +```text +---------+ | class | +---------+ @@ -273,7 +274,7 @@ https://leetcode.com/problems/duplicate-emails/description/ 邮件地址表： -```html +```text +----+---------+ | Id | Email | +----+---------+ @@ -285,7 +286,7 @@ https://leetcode.com/problems/duplicate-emails/description/ 查找重复的邮件地址： -```html +```text +---------+ | Email | +---------+ @@ -331,7 +332,7 @@ https://leetcode.com/problems/delete-duplicate-emails/description/ 邮件地址表： -```html +```text +----+---------+ | Id | Email | +----+---------+ @@ -343,7 +344,7 @@ https://leetcode.com/problems/delete-duplicate-emails/description/ 删除重复的邮件地址： -```html +```text +----+------------------+ | Id | Email | +----+------------------+ @@ -413,7 +414,7 @@ https://leetcode.com/problems/combine-two-tables/description/ Person 表： -```html +```text +-------------+---------+ | Column Name | Type | +-------------+---------+ @@ -426,7 +427,7 @@ PersonId is the primary key column for this table. Address 表： -```html +```text +-------------+---------+ | Column Name | Type | +-------------+---------+ @@ -483,7 +484,7 @@ https://leetcode.com/problems/employees-earning-more-than-their-managers/descrip Employee 表： -```html +```text +----+-------+--------+-----------+ | Id | Name | Salary | ManagerId | +----+-------+--------+-----------+ @@ -531,7 +532,7 @@ https://leetcode.com/problems/customers-who-never-order/description/ Customers 表： -```html +```text +----+-------+ | Id | Name | +----+-------+ @@ -544,7 +545,7 @@ Customers 表： Orders 表： -```html +```text +----+------------+ | Id | CustomerId | +----+------------+ @@ -555,7 +556,7 @@ Orders 表： 查找没有订单的顾客信息： -```html +```text +-----------+ | Customers | +-----------+ @@ -624,7 +625,7 @@ https://leetcode.com/problems/department-highest-salary/description/ Employee 表： -```html +```text +----+-------+--------+--------------+ | Id | Name | Salary | DepartmentId | +----+-------+--------+--------------+ @@ -637,7 +638,7 @@ Employee 表： Department 表： -```html +```text +----+----------+ | Id | Name | +----+----------+ @@ -648,7 +649,7 @@ Department 表： 查找一个 Department 中收入最高者的信息： -```html +```text +------------+----------+--------+ | Department | Employee | Salary | +------------+----------+--------+ @@ -706,7 +707,7 @@ https://leetcode.com/problems/second-highest-salary/description/ ### Description -```html +```text +----+--------+ | Id | Salary | +----+--------+ @@ -718,7 +719,7 @@ https://leetcode.com/problems/second-highest-salary/description/ 查找工资第二高的员工。 -```html +```text +---------------------+ | SecondHighestSalary | +---------------------+ @@ -791,7 +792,7 @@ https://leetcode.com/problems/rank-scores/description/ 得分表： -```html +```text +----+-------+ | Id | Score | +----+-------+ @@ -806,7 +807,7 @@ https://leetcode.com/problems/rank-scores/description/ 将得分排序，并统计排名。 -```html +```text +-------+------+ | Score | Rank | +-------+------+ @@ -851,7 +852,7 @@ ORDER BY |1| 4.1 |2| 4.2| |1| 4.1 |3| 4.3| -可以看到每个 S1.score 都有对应好几条记录，我们再进行分组，并统计每个分组的数量作为 'Rank' +可以看到每个 S1.score 都有对应好几条记录，再进行分组，并统计每个分组的数量作为 'Rank' ```sql SELECT @@ -887,7 +888,7 @@ ORDER BY | 4.2 | 2 | | 4.1 | 3 | -而我们希望的结果为： +而希望的结果为： | score | Rank | | :---: | :--: | @@ -907,7 +908,7 @@ ORDER BY | 1 | 4.1 | 2 | 4.2 | | 1 | 4.1 | 1 | 4.1 | -我们想要的结果是，把分数相同的放在同一个排名，并且相同分数只占一个位置，例如上面的分数，Id=2 和 Id=3 的记录都有相同的分数，并且最高，他们并列第一。而 Id=1 的记录应该排第二名，而不是第三名。所以在进行 COUNT 计数统计时，我们需要使用 COUNT( DISTINCT S2.score ) 从而只统计一次相同的分数。 +想要的结果是，把分数相同的放在同一个排名，并且相同分数只占一个位置，例如上面的分数，Id=2 和 Id=3 的记录都有相同的分数，并且最高，他们并列第一。而 Id=1 的记录应该排第二名，而不是第三名。所以在进行 COUNT 计数统计时，需要使用 COUNT( DISTINCT S2.score ) 从而只统计一次相同的分数。 ```sql SELECT @@ -948,7 +949,7 @@ https://leetcode.com/problems/consecutive-numbers/description/ 数字表： -```html +```text +----+-----+ | Id | Num | +----+-----+ @@ -964,7 +965,7 @@ https://leetcode.com/problems/consecutive-numbers/description/ 查找连续出现三次的数字。 -```html +```text +-----------------+ | ConsecutiveNums | +-----------------+ @@ -1013,7 +1014,7 @@ https://leetcode.com/problems/exchange-seats/description/ seat 表存储着座位对应的学生。 -```html +```text +---------+---------+ | id | student | +---------+---------+ @@ -1027,7 +1028,7 @@ seat 表存储着座位对应的学生。 要求交换相邻座位的两个学生，如果最后一个座位是奇数，那么不交换这个座位上的学生。 -```html +```text +---------+---------+ | id | student | +---------+---------+ @@ -1091,3 +1092,8 @@ VALUES ( '4', 'Green' ), ( '5', 'Jeames' ); ``` + +## 参考资料 + +- [LeetCode 数据库题库](https://leetcode.com/problemset/database/) +- [MySQL 8.0 Reference Manual](https://dev.mysql.com/doc/refman/8.0/en/)