Question

sql 查找表里 字段是否有相同记录怎么查？

查找表 tab 里面 字段aa字段是否有相同记录，sql怎么查

Answer 1

select aa,count(*) from tab group by aa having count(*)>=2

Answer 2

select * from tab a
where exists(select 1 from tab b where a.主键<>b.主键 and a.aa=b.aa)

Answer 3

select * from tab where aa in(
select aa from tab group by aa having count(1)>1
)