Mysql之运算的使用

比较运算符

Select shohin_mei,shohin_bunrui from shohin where hanbai_tanka = 500;

--选出列为500的记录

Select shohin_mei,shohin_bunrui from shohin where hanbai_tanka <> 500;

--选出列不是500的记录

可以使用的比较运算符= 、<>、>=、>、<=、<

Select shohin_id,shohin_bunrui from shohin where hanbai_tanka >= 1000;

Ps:注意不能对NULL进行比较运算符。

---选取不为NULL的记录

Select shohin_mei,shiire_tanka from shohin where shiire_tanka is not NULL;

逻辑运算符

NOT:select shohin_mei,shohin_bunrui from Shohin where not banbai_tanka >= 1000;

And（&&） 与OR（||）

Select shohin_mei,shiire_tanka from shohin where shohin_bunrui = ‘厨房用具’ and hanbai_tanka >= 3000;

Select shohin_mei,shiire_tanka from shohin where shohin_bunrui = ‘厨房用具’ or hanbai_tanka >= 3000;

Select shohin_mei,shohin_bunrui,torokubi from shohin

Where shohin_burui = ‘日用品’ and ( torokubi = ‘2009-09-11’ or torokubi = ‘2009-09-20’);

----这里（）的优先级是大于and的，而and单独的优先级是大于or的