Oracle SQL ORA-00937：不是单组功能

Question

我想搜索类型为“Savings”的帐户，但以下代码段提供了错误“ORA-00937：不是单个组组功能“ - 有谁知道为什么我得到这个错误？

SELECT b.bID as "Branch Number", COUNT(a.accNum) as "# of Saving Accounts" 
from branchtable b, accounttable a 
where a.bId = b.bID 
and a.acctype = 'Savings'; 

Answer 1

你需要一个 “GROUP BY” 子句：

SELECT b.bID as "Branch Number", 
    COUNT(a.accNum) as "# of Saving Accounts" 
from 
    branchtable b, accounttable a 
where 
    a.bId = b.bID and a.acctype = 'Savings' 
group by b.bID; 

Answer 2

SELECT b.bID as "Branch Number", COUNT(a.accNum) as "# of Saving Accounts" 
from branchtable b, accounttable a 
where a.bId = b.bID 
and a.acctype = 'Savings' 
GROUP BY b.bID; 

PS：你除了聚合函数SELECT子句中使用哪种列应该出现在GROUP BY clause.It的一个盲目的规则。