MySQL 常用知识记录

原理:ORDER BY RAND() 能够把数据随机排序，也可分页查询limit 2 .

SELECT * from t_movie_info ORDER BY RAND();

create table t_movie_info(
movie_id INT,
movie_name VARCHAR(64),
movie_type VARCHAR(16)
)
insert into t_movie_info VALUES(‘1’,‘幸福来敲门’,‘励志型’);
insert into t_movie_info VALUES(‘2’,‘倚天屠龙记’,‘武侠型’);
insert into t_movie_info VALUES(‘3’,‘大理寺办案’,‘武侠型’);
insert into t_movie_info VALUES(‘4’,‘栀子花开吖’,‘爱情型’);
insert into t_movie_info VALUES(‘5’,‘贫民窟男人’,‘励志型’);

SELECT * from t_movie_info;

1.添加索引

ALTER table t_movie_info add PRIMARY key (movie_id);

2.查看索引

show INDEXes FROM t_movie_info;

3.删除索引

ALTER table t_movie_info drop INDEX movie_id;

4.增加列

ALTER TABLE t_movie_info add COLUMN movie_Job VARCHAR(20);

5.删除列

ALTER TABLE t_movie_info DROP COLUMN movie_Job;

6.更新一列

UPDATE t_movie_use set src_file_day = ‘2018-05-02’ where uid =‘103’

7.加入一条数据

insert into t_movie_use VALUES(‘2019-10-30 2:17:30’,‘2019-10-30’,‘101’,1001,‘001’,‘40’);

8.流程控制函数

select movie_id AS 电影编号,
CASE WHEN movie_id <=3 THEN ‘好看’
WHEN movie_id >= 4 THEN ‘凑合’
ELSE ‘垃圾电影’ END AS 审核,
movie_name AS 电影名称,
movie_type AS 电影类型
from t_movie_info ORDER BY movie_id desc;

扫描二维码关注公众号，回复： 10970521 查看本文章

9.用来自符串拼接。

select CONCAT(‘詹姆斯’,‘NBA’)AS 你强啊;

10.通过它可以查看到SQL耗费时间

show PROFILES;

11.查看现在的时间

SELECT NOW();

12. #新增多条记录

 insert into LM(ID ,NAME ,age,sex)VALUES(201,'小一',12,'女'),(202,'小二',18,'女'),(203,'小五',19,'女');