1.查看MySQL版本

select version();

2.快速复制表结构，不包含相关主键及约束

create table user_test as select * from user where 1=2;

3.uuid

select uuid(),uuid_short();

4.替换uuid()里的’-‘为’’

select replace(uuid(),'-','');

5.md5摘要

select md5(uuid()),md5('123456');

6.复制数据

insert into user_test(id, name, age, city) 
select replace(uuid(),'-',''),name,age,'vue3' from user;

insert into user_test(id, name, age, city) 
select md5(uuid()),name,25,city from user;

7.ip4地址转整数，整数转换ip4地址

select INET_ATON('127.0.0.1') address_2_number,
INET_NTOA(2130706433) number_2_address;

8.删除数据，不允许边查询边删除/更新。

delete from user_test where id in (select id from user_test where parent_id='75e2f86d0a2c11ee89c70242ac110002');
-- [HYO00][1093] You can't specify target table 'user_test' for update in FROM clause
delete from user_test where id in (select id from (select id from user_test where parent_id='75e2f86d0a2c11ee89c70242ac110002') t);

9.查询数据库blob字段

select convert(remark using utf8) from user

10.关联查询，没有数据的统计为0，构造基础数据，子查询或连接查询实现

select l.province,ifnull(
    (select biz.num from (
        select '北京' as province,100 as num
        union all
        select '深圳' as province,208 as num
    ) biz where biz.province = l.province),0) as num
from (select '北京' as province
      union all
      select '上海'
      union all
      select '广州'
      union all
      select '深圳') l