sql - 错误单行子查询返回多行

Question

此查询返回数据集合。但我只需要客户名单。

select * from customer where cust_acnt_nbr = (select cust_acnt_nbr from Asset where dstrct_id = (select dstrct_id from dstrct where dstrct_nm = 'ATLANTA'))

请帮我获取客户名单

Answer 1

如果子查询可以返回多行，则使用in代替：=

select * from customer where cust_acnt_nbr IN
    (select cust_acnt_nbr from Asset where dstrct_id IN
        (select dstrct_id from dstrct where dstrct_nm = 'ATLANTA'))

Answer 2

我尽量避免使用子查询，因为它们的性能可能很差，并且不清楚您要实现的目标。您通常可以将其转换为一系列更易于阅读的简单连接。

select c.* 
from customer c
inner join Asset a on c.cust_acnt_nbr = a.cust_acnt_nbr 
inner join dstrct d on d.dstrct_id =a.dstrct_id 
where dstrct_nm = 'ATLANTA'