sql - 如何正确编码 INSERT 子查询？

Question

我测试了 SQL 的每个部分，它工作正常。

但是，我的WHERE条款有问题..在 VS 2012 中设置断点并没有得到太多细节...

这应该如何成为INSERT使用 MS SQL SERVER 的子查询语句的代码？

INSERT INTO Emails (email, insertDate) 
VALUES (@Email, @DateToday) 
WHERE NOT EXISTS (SELECT Emails.email 
                  FROM Emails WHERE Emails.email = @Email);

Answer 1

INSERT INTO Emails (email, insertDate) 
SELECT @Email, @DateToday
WHERE NOT EXISTS (SELECT Emails.email 
                  FROM Emails WHERE Emails.email = @Email);

Answer 2

这将起作用

INSERT INTO Emails (email, insertDate) 
SELECT @Email, @DateToday
WHERE NOT EXISTS (SELECT Emails.email 
                  FROM Emails WHERE Emails.email = @Email)

但更好的解决方案可能是电子邮件列上的唯一索引

Answer 3

尝试使用如下：

"INSERT INTO Emails (email, insertDate) VALUES ('@Email', '@DateToday') WHERE NOT EXISTS (SELECT Emails.email FROM Emails WHERE Emails.email = '@Email');"

Answer 4

INSERT INTO Emails (email, insertDate) 
SELECT Email, DateToday
WHERE NOT EXISTS (SELECT Emails.email 
                  FROM Emails WHERE Emails.email = Email)

它将工作设置email为非空列或唯一索引。