我有两个sql查询，其中一个我执行左外连接，两者都应返回相同的记录数，但两个sql查询中返回的行数不同
select Txn.txnRecNo
from Txn
inner join Person on Txn.uwId = Person.personId
full outer join TxnInsured on Txn.txnRecNo = TxnInsured.txnRecNo
left join TxnAdditionalInsured on Txn.txnRecNo = TxnAdditionalInsured.txnRecNo
where Txn.visibleFlag=1
and Txn.workingCopy=1
返回20条记录
select Txn.txnRecNo
from Txn
inner join Person on Txn.uwId = Person.personId
full outer join TxnInsured on Txn.txnRecNo = TxnInsured.txnRecNo
where Txn.visibleFlag=1
and Txn.workingCopy=1
返回15条记录
最佳答案
我怀疑 TxnAdditionalInsured 表有重复记录。使用不同
select distinct Txn.txnRecNo
from Txn
inner join Person on Txn.uwId = Person.personId
full outer join TxnInsured on Txn.txnRecNo = TxnInsured.txnRecNo
left join TxnAdditionalInsured on Txn.txnRecNo = TxnAdditionalInsured.txnRecNo
where Txn.visibleFlag=1
and Txn.workingCopy=1
关于sql - 在左连接上返回不同的行数，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/35885169/