如果存在，然后使用INSERT，SQL Server进行ELSE

Question

我之前的问题最终没有回答我的长期问题，这是：

我需要将User_Passwords密码（ up_Password ）与传入的新密码（ @CurrentPassword ）进行比较。 如果他们匹配，我需要返回一个1这样的代码遵循不同的轨迹，而如果它是一个新的密码，它会被INSERTed到表中。 这是我认为正在执行的存储过程部分：

DECLARE @UserNumberOfPasswords INT
DECLARE @ua_pk uniqueidentifier
DECLARE @ResetDaysAmount INT
DECLARE @AllowedNumberOfPasswords INT
DECLARE @CurrentPasswordDate DATE
DECLARE @CurrentPassword varchar(25)

SELECT *
FROM dbo.User_Passwords
WHERE ua_fk = @ua_pk
ORDER BY up_PasswordDate DESC

DELETE FROM User_Passwords
WHERE @ua_pk = ua_fk
AND @CurrentPasswordDate > (DATEADD(DAY, (@ResetDaysAmount - 1), up_PasswordDate))

SELECT *
FROM dbo.User_Passwords
WHERE ua_fk = @ua_pk
ORDER BY up_PasswordDate ASC

SELECT @UserNumberOfPasswords = COUNT(*)    
FROM User_Passwords AS up
WHERE ua_fk = @ua_pk

IF @UserNumberOfPasswords > @AllowedNumberOfPasswords
BEGIN
    WITH T
    AS (SELECT TOP (@UserNumberOfPasswords - @AllowedNumberOfPasswords) *
        FROM   User_Passwords
        WHERE  ua_fk = @ua_pk
        ORDER BY up_PasswordDate ASC)
    DELETE FROM T; 
END

IF @UserNumberOfPasswords = @AllowedNumberOfPasswords
BEGIN
    WITH T
    AS (SELECT TOP 1 *
        FROM User_Passwords
        WHERE ua_fk = @ua_pk
        ORDER BY up_PasswordDate ASC)
    DELETE FROM T;
END

IF EXISTS 
    (SELECT 1
    FROM User_Passwords
    WHERE up_Password = @CurrentPassword)
    SELECT 1
ELSE
    INSERT INTO User_Passwords (ua_fk, up_Password, up_PasswordDate)
    VALUES (@ua_pk, @CurrentPassword, @CurrentPasswordDate

我已经做了很多测试，得出的结论是，它总是返回1 ，但我不确定为什么。

底线-我想比较值，如果值相等，请使用一个值返回VB.Net，以便可以将其用于不同的代码路径，而如果它们不相等，则将其添加到表，然后返回到我的VB.Net代码。

Answer 1

DECLARE @result integer;   

IF EXISTS         (SELECT 1
                   FROM User_Passwords
                   WHERE up_Password = @CurrentPassword)
  BEGIN
    SET @result = 1;
  END;
ELSE
 BEGIN
    INSERT INTO User_Passwords (ua_fk, up_Password, up_PasswordDate)
    VALUES (@ua_pk, @CurrentPassword, @CurrentPasswordDate);
    SET @result = 0;
 END;

RETURN @result;

Answer 2

代替

IF EXISTS 
    (SELECT 1
    FROM User_Passwords
    WHERE up_Password = @CurrentPassword)
    SELECT 1
ELSE
    INSERT INTO User_Passwords (ua_fk, up_Password, up_PasswordDate)
    VALUES (@ua_pk, @CurrentPassword, @CurrentPasswordDate

不是吗

IF EXISTS 
    (SELECT 1
    FROM User_Passwords
    WHERE up_Password = @CurrentPassword
    AND   ua_fk = @ua_pk ) //Only search for passwords that belong to this user
    SELECT 1
ELSE
    INSERT INTO User_Passwords (ua_fk, up_Password, up_PasswordDate)
    VALUES (@ua_pk, @CurrentPassword, @CurrentPasswordDate

...？

否则，如果任何用户（不仅是感兴趣的用户）都存在密码，则存储过程将返回1，这可能会解释您的结果。

Answer 3

如果需要调试，我通常会添加打印件

IF EXISTS 
    (SELECT 1
    FROM User_Passwords
    WHERE up_Password = @CurrentPassword)
    BEGIN
        PRINT ('EXISTS')
        PRINT ('up_Password:' + up_Password)
        PRINT ('@CurrentPassword:' + @CurrentPassword)
    SELECT 1
    END
ELSE
    BEGIN
        PRINT ('NOT EXISTS')
        PRINT ('up_Password:' + up_Password)
        PRINT ('@CurrentPassword:' + @CurrentPassword)
        INSERT INTO User_Passwords (ua_fk, up_Password, up_PasswordDate)
        VALUES (@ua_pk, @CurrentPassword, @CurrentPasswordDate)
    END