mysql的字符串连接符
mysql> select CONCAT('My', 'S', 'QL');
减去一天SELECT DATE_SUB(CURDATE(), INTERVAL 1 DAY);减去一个小时hour(now())-1...
select count(id),字段from 表名 group by字段 having count(字段)>1;...
SELECT product_brand FROM shop_product WHERE LENGTH(product_brand)>...
DATE_ADD(now(),INTERVAL 1 DAY);...
truncate table 表名...
SELECT CURDATE()当天日期...