Question

sql 表aaa有若干字段a,b,c,只用一条sql语句,完成统计分别a=1,2,3；b=1,2,3；c=1,2,3

Answer 1

可以参考下列SQL语句，一次性输出3个字段的各自的合计数，只汇总那3个字段的值分别为1,2,3的记录

select sum(t.a) as sumA,sum(t.b) as sumB,
sum(t.c) as sumC from
(select a,0 as b, 0 as c from aaa where a in (1,2,3)
union all
select 0,b, 0 from aaa where b in (1,2,3)
union all
select 0,0, c from aaa where c in (1,2,3)) t