求一简单查询

Question

select
(select sum(to_number(工资))  from table1 where 班组 in('一班')) -
(select sum(to_number(工资))  from table1 where 班组 in('二班')) from dual

Answer 1

or:
select a.一班工资 - b.二班工资 from 
(select sum(to_number(工资)) 一班工资 from table1 where 班组 in('一班')) a ,
(select sum(to_number(工资))  二班工资 from table1 where 班组 in('二班')) b 

Answer 2

保留两位小数,四舍五入
select round(321.456,2) from dual
32.46
取整，四舍五入
select round(321.556) from dual
33
取整，截掉 小数部分
select trunc(321.556,2) from dual
32

Answer 3

select round( sum(decode(班组,'一班',工资,0))-sum(decode(班组,'二班',工资,0)),2)
from yourTable

Answer 4

保留两位小数:
trunc(a,2):按位截取
round(a,2):按位四舍五入

Answer 5

select round( sum(decode(班组,'一班',to_number(工资),-1*to_number(工资))),2)
from yourTable