Mysql题目篇

1.增

1.1为表中指定字段添加数据

INSERT INTO 表名（字段名1，字段名2，…）VALUES（值1，值2，…）

INSERT INTO `user`(id,role) VALUES(3,"admin");

1.2为表中所有字段添加数据（可以不指名字段）

INSERT INTO 表名 VALUES(值11，值2，…）；

INSERT INTO `user` VALUES(5,"lsy","lsy1234","admin");

1.3同时添加多条数据

INSERT INTO `user` VALUES(6,"lsy","lsy1234","admin"),
                         (7,"lsy7","lsy1234","admin"),
                         (8,"lsy8","lsy1234","admin");

2.删

2.1删除部分数据

DELETE from user where username="lsy"

2.2删除所有数据

DELETE from user 

3.改

3.1修改部分数据

UPDATE user set role="admin1" where id=9

3.2修改全部数据

UPDATE user set role="admin2" 

4.查

4.1简单查询

select id,role from user
select * from user
select id,role from user where id<10
select id,role from user where id in (9,10)
select id,role from user where id BETWEEN 2 and 10
select id,role from user where role is NULL
select id,role from user where role like "adm%"（%匹配任意长度的字符串，包括空字符串。）
select id,role from user where role like "adm_"（下划线通配符只匹配单个字符）
select id,role from user where role like "admi_" and username="shiro"（AND 的优先级高于 OR）
select id,role from user where role like "admi_" or username="shiro"

4.2高级查询

SELECT COUNT(*) FROM user
SELECT sum(id) FROM user
SELECT avg(id) FROM user
SELECT max(id) FROM user
SELECT min(id) FROM user
SELECT *from user order by id DESC
SELECT COUNT(*) ,gender FROM user GROUP BY gender;
SELECT sum(grade),gender FROM user GROUP BY gender HAVING SUM(grade) < 300;
SELECT * from user   LIMIT 2 

4.3子查询

SELECT * FROM user where id=(SELECT MAX(id) from user)
SELECT * FROM (SELECT MAX(id) from user) as user1

4.4表连接

SELECT * FROM user u INNER JOIN role r on u.id=r.id 
SELECT * FROM user u LEFT JOIN role r on u.id=r.id 
SELECT * FROM user u RIGHT JOIN role r on u.id=r.id 
SELECT * FROM user u LEFT JOIN role r on u.id=r.id UNION SELECT * FROM user u RIGHT JOIN role r on u.id=r.id