二刷leetcode MYSQL基础题库 最近二刷leetcode SQL的基础题库(家境贫寒,买不起会员o(╥﹏╥)o),记录一下比较有意思的题目。 以下题目均来自:力扣(LeetCode)链接: 力扣。1.部门工资最高的员工难度:中等 Employe… 陈罐头 刷完LeetCode数据库题,对知识点做个总结 Excel...发表于SQL知识... 谷歌大佬所撰《Lee...
方法二:连接查询筛选出有效订单记录集合 https://leetcode-cn.com/problems/trips-and-users/solution/san-chong-jie-fa-cong-nan-dao-yi-zong-you-gua-he-n/ 计算订单取消率还可以用avg(Status!='completed'): https://leetcode-cn.com/problems/trips-and-users/solution/ci-ti-bu-nan-wei-fu-za-er-...
网址：https://leetcode-cn.com/当然还有几个其它的，像 SQLZOO、SQLBolt 也不错，就不在这展开说了...
1 SELECT question_id AS survey_log 2 FROM 3 (SELECT 4 question_id, 5 SUM(IF(action='answer',1,0)) as answer_num, 6 SUM(IF(action='show',1,0))as show_num 7 -- SUM(case when action="answer" THEN 1 ELSE 0 END) AS num_answer, 8 -- SUM(case when action="show" THEN 1 ...
Explanation:The CASE statement is used to categorize employees based on their salary. The result categorizes them as “High”, “Medium”, or “Low”. 19. Find Duplicate Records Question: Write a query to find duplicate email addresses from the users table. Assume the users table has a colu...
使用SQL练习平台:利用如LeetCode这样的在线练习平台,通过解决实际问题来巩固你的SQL技能。 3. 掌握SQL高级功能如聚合、连接和子查询 学习聚合函数:如COUNT()、SUM()、AVG()等,用于对查询结果进行汇总分析。 掌握连接(JOIN)操作:学习不同类型的连接(如INNER JOIN、LEFT JOIN、RIGHT JOIN等),以便从多个表中合并数据...
Structured Query Language (SQL) is the most commonly used programming language for querying and managing data in relational databases. The solution is for the corresponding LeetCode SQL question. - Annahcj/SQL-MySQL-Solutions
Here’s also the code output. 2. Count Student Number in Departments The question from LeetCode asks you the following. “Write an SQL query to report the respective department name and number of students majoring in each department for all departments in theDepartmenttable (even ones with no...
qd.difficult_level, COUNT(qpd.question_id) / COUNT(DISTINCT qpd.device_id) FROM question_practice_detail qpd left JOIN user_profile up on up.device_id = qpd.device_id left JOIN question_detail qd on qpd.question_id = qd.question_id WHERE up.university = '山东大学' GROUP BY qd.dif...
7.578. Get Highest Answer Rate Question 善用order by 将query写的简洁一些 注意null是不计算在count以内的 善用if 函数 if(条件,条件为真值,条件不为真值) 简洁版:SELECT question_id AS 'survey_log' FROM survey_log GROUP BY question_id ORDER BY COUNT(answer_id) / COUNT(IF(action = 'show', 1...