MySQL 几个比较重要的用法总结

ALTER TABLE `t_areadivision` ADD INDEX code (`code`);

update t_taobao_region t left join t_areadivision a on t.region_code = a.code set t.parent = a.id;

unix_timestamp(now())

update t_areadivision set parent = -10 where id in (select id from (select id,count(*) sum from t_areadivision group by parent,name having sum > 1) id

select id,count(*) sum from t_areadivision group by parent,name having sum > 1

SELECT studentNO FROM student WHERE (studentNO,name) = (SELECT studentNO,name FROM student WHERE name='李四')