mysql操作

1、字符转Decimal

CAST(column AS DECIMAL(9,2))

2、将计算结果取两位小数：

round(column, 2)

3、查询非空 

select * from table_XX where id is not null;

4、连表update更新

update a inner join (select yy from b) c on a.id =c.id set a.xx = c.yy