2023-07-16 09:34
149
0
0
0
UNION：求两个或多个集合的并集，去除重复
UNION ALL：求两个或多个集合的并集，不去除重复
INTERSECT：求两个或多个集合的交集，去除重复
MINUS：求两个或多个集合的差集，去除重复
2023-07-16 09:34
153
0
0
0
SELECT * FROM student WHERE MONTH(birthday) = MONTH(DATE_ADD(NOW(), INTERVAL 1 MONTH));
2023-07-16 09:34
126
0
0
0
select distinct student_id
from student_course
group by student_id
having count(*) >= 2;
2023-07-15 08:49
127
0
0
0
MySQL 和 MongoDB 是两种不同的关系型和非关系型数据库管理系统（RDBMS 和 NoSQL）。
MySQL 是一种关系型数据库管理系统，它依赖于表的概念来组织数据，使用 Structured Query Language (SQL) 作为其查询语言。它的特点是结构化、可靠性强、事务性好，适合于存储和查询关系数据，比如账号、订单等。
Mon
2023-07-15 08:48
126
0
0
0
SELECT t1.name, t1.grade
FROM table1 t1
INNER JOIN
(
SELECT class, MAX(grade) AS max_grade
FROM table1
GROUP BY class
) t2
ON t1.class = t2.class AND t1.grade =
2023-07-15 08:48
140
0
0
0
SELECT s.name, g.score
FROM student AS s
INNER JOIN grade AS g ON s.id = g.student_id
INNER JOIN course AS c ON g.course_id = c.id
WHERE c.teacher_name = '张三'
ORDER BY g.score
2023-07-14 09:07
132
0
0
0
SELECT sno,AVG(score)
FROM student
WHERE score < 60
GROUP BY sno
HAVING COUNT(score)>=2;
2023-07-14 09:06
158
0
0
0
SELECT a.student_no, a.course_no, a.score
FROM student_score a
INNER JOIN student_score b
ON a.score=b.score
WHERE a.course_no b.course_no;