Question

我的where exists条款不起作用。我错过了什么微不足道的事情？

select * from patient as p
where exists
(
    select p.patientid, count(*) from tblclaims as c 
    inner join patient as p on p.patientid=c.patientid
    and p.admissiondate = c.admissiondate
    and p.dischargedate = c.dischargedate
    group by p.patientid
    having count(*)>500
)

患者和tblclaims通过三字段复合键连接在一起，如您在查询中所见。

Answer 1

count(*) from tblclaims as c是不必要的，可能会抛弃查询。

此外，您没有WHERE条款加入patient p条款{/ 1}}。

更不用说你在主查询和exists子句中使用p作为别名，这只是令人困惑。

您可能需要以下内容：

exists

Answer 2

您根本不需要在子查询中使用内部联接;这实际上是你额外结果的原因。您应该在外部查询中引用“p”。

select * from patient as p
where exists
(
    select 1 from tblclaims as c 
    where p.patientid = c.patientid
       and p.admissiondate = c.admissiondate
       and p.dischargedate = c.dischargedate
    group by c.patientid
    having count(*)>500
)

Answer 3

我不太喜欢存在。也许你可以使用其他功能。试试这个：

select * from patient as p
where patientid IN
(
    select p.patientid from tblclaims as c 
    inner join patient as p on p.patientid=c.patientid
    and p.admissiondate = c.admissiondate
    and p.dischargedate = c.dischargedate
    group by p.patientid
    having count(*)>500
)

存在返回所有行的位置

3 个答案: