Question

SQL 同一张表里同字段比对

如：TAB1 中有字段ID1、ID2、QTY
ID1 ID2 QTY
1 a 20
1 a 30
2 b 90
2 c 20
当ID1的值相等时，再看ID2的值，如果ID2的值也相等时就把字段QTY求和

Answer 1

select id1,id2,sum(qty) 总和
from tab1
group by id1,id2 having count(ID2)>1;

Answer 2

select id1,id2,sum(qty) 总和
from tab1
group by id1,id2;

Answer 3

select id1,id2,sum(qty) 总和
from tab1
group by id1,id2 having count(ID2)>1