MYSQL 中,进行空值的判断:
判断某个字段是否为空
isnull 判断是否为空:
只有当字段为null时,isnull()返回1,空串和有数据都为0
select * from user where ISNULL(name)=1;
is not null
select * from user where name is not null;
判断某个字段是否为空串
select goods_id,item_code from goods_info where LENGTH(trim(item_code))>0