mysql常用

1.查询行号

SELECT @rowno:=@rowno+1 as rowno,t.* from xxx t,(select @rowno:=0) r;

参考：https://blog.csdn.net/muzizhuben/article/details/49449853

2.随机取数据

SELECT * FROM xxx WHERE ... ORDER BY RAND() LIMIT 10000;

3.ddl

查看结构 DESC `xxx`;

查看索引 SHOW INDEX FROM `xxx`;

添加索引 ALTER TABLE `xxx` ADD INDEX `idx_xxx` (`xxx`);

增加列 ALTER TABLE `xxx` ADD COLUMN `xxx` INT COMMENT 'xxx' AFTER `xxx`;

4.mysql 按 in 排序

select * from ttt where aa in (1,2,3) order by field (aa,1,2,3);

参考：https://blog.csdn.net/wwwyuanliang10000/article/details/37660545

5.逗号分隔

SELECT GROUP_CONCAT(id) FROM aa WHERE xxx IN (21);

6.日期格式化 yyyy-MM-dd HH:mm:ss

select DATE_FORMAT(NOW(),'%Y-%m-%d %H:%i:%s')

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bigint(10)和bigint(20)的区别 https://www.cnblogs.com/dragoncn/p/6594228.html