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题解 | #确定已售出产品项 BR01 的总数#

SELECT SUM(quantity) items_ordered FROM OrderItems WHERE prod_id = 'BR01' 题解：1.任务：总数2.产品id为BR01思路：1.查询时使用求和函数，因为不一定只有一条是指定的记录2.条件限制

2023-10-02

2 425

题解 | #返回 2020 年 1 月的所有订单#

SELECT order_num, order_date FROM Orders WHERE YEAR(order_date) = '2020' AND MONTH(order_date) = '01' ORDER BY order_date 题解：1.查询订单号和订单日期2.限制条件：20201...

2023-10-02

0 338

题解 | #顾客登录名#

SELECT cust_id, cust_name, UPPER(CONCAT(LEFT(cust_contact,2),LEFT(cust_city,3))) user_login FROM Customers 题解：1.任务：查询用户登录名，由两个字段的不同部分组成，最后要大写思路：1.查询...

2023-10-02

0 287

题解 | #检索产品名称和描述（一）#

SELECT prod_name, prod_desc FROM Products WHERE prod_desc LIKE('%toy%') 字符串匹配的题题解：1.任务：检索产品名和描述2.限制：描述中包含toy思路：1.检索字段2.使用like匹配目标字符串

2023-10-02

0 404

题解 | #21年8月份练题总数#

SELECT COUNT(DISTINCT device_id) did_cnt, COUNT(question_id) question_cnt FROM question_practice_detail WHERE date BETWEEN '2021-08-01' AND '2021-...

2023-10-01

0 241

题解 | #浙大不同难度题目的正确率#

SELECT c.difficult_level, COUNT(CASE WHEN b.result = 'right' THEN 1 ELSE NULL END)/COUNT(b.device_id) correct_rate FROM user_profile a, quest...

2023-10-01

0 256

题解 | #统计复旦用户8月练题情况#

SELECT u.device_id, u.university, COUNT(CASE WHEN q.question_id THEN 1 ELSE NULL END) question_cnt, SUM(CASE WHEN q.result = 'right' THEN 1 ELSE 0...

2023-10-01

0 248

题解 | #找出每个学校GPA最低的同学#

SELECT b.device_id, b.university, b.gpa FROM ( SELECT device_id, university, ROW_NUMBER() OVER(PARTITION BY university ORDER BY gpa) rak, gpa FROM us...

2023-10-01

0 316

题解 | #找出每个学校GPA最低的同学#

SELECT a.device_id, a.university, a.gpa FROM user_profile a, ( SELECT device_id, university, ROW_NUMBER() OVER(PARTITION BY university ORDER BY gpa) r...

2023-10-01

3 489

题解 | #截取出年龄#

SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(profile, ',', -2),',',1) age, COUNT(*) number FROM user_submit GROUP BY age;

2023-10-01

0 196