Question

如何在插入之前检查值是否存在？

INSERT INTO DeliveryOrder (ContactName, ContactID) VALUES ('Andy', (SELECT ContactID FROM Contact WHERE ContactName = 'Andy'))

我想在插入记录之前验证ContactID是否存在。

尝试以下但不工作：

INSERT INTO DeliveryOrder (ContactName, ContactID) VALUES ('Andy', (SELECT ContactID FROM Contact WHERE ContactName = 'Andy')) WHERE IF Exists (SELECT ContactID FROM Contact WHERE ContactName = 'Andy')

Answer 1

INSERT INTO DeliveryOrder (ContactName, ContactID)
 select 'Andy', ContactID
   from Contact
  WHERE ContactName = 'Andy'

Answer 2

这会对你有所帮助

IF  EXISTS (SELECT ContactID
        FROM Contact  c
        WHERE
            c.ContactName ='Andy'
        )
Insert Into DeliveryOrder (ContactName, ContactID)
        VALUES ('Andy', (SELECT top 1 ContactID FROM Contact WHERE ContactName = 'Andy'))

试试这个

在SQL，SQLite中存在与IF存在的INSERT

2 个答案: