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