Mysql操作

having和where的区别

having（字段）用于查询查询出来的字段；
where (字段） 用于查询纯在数据库的字段。

• having和where都可以使用的情况
  select goods_price,goods_name,goods_number from sw_goods where goods_price >100;
select goods_price,goods_name,goods_number from sw_goods having goods_price >100;

• 只能使用where不能使用having的情况
  SELECT goods_name,goods_number from sw_goods where goods_price>100;
SELECT goods_name,goods_number from sw_goods where goods_price>100;

• 只能使用having不能使用where的情况
  SELECT goods_category_id,avg(goods_price) as avg FROM sw_goods GROUP BY goods_category_id having avg>100;