考慮在查詢中爲空字符串爲空

Question

我正在使用sql server R2。我有一個存儲過程，其中我傳遞了兩個參數@username varchar(100)和@password varchar(100)。

現在，當我從我的應用程序第一次創建用戶時，密碼將爲NULL。

我想做一個查詢，返回匹配用戶名和密碼的記錄。問題是代碼正在通過empty string到stored procedure。我想要自動考慮或轉換empty string to NULL的內容。我已經有這個解決方案使用if condition但我想使用單個查詢，而不是條件。

編輯：

它是一個簡單的存儲過程：

CREATE PROCEDURE [dbo].[Pro_TblP] 
(
@userName varchar(100), 
@password varchar(100) 
) 
AS 
BEGIN 
    IF (@password ='') 
     BEGIN 
      SELECT * FROM TblP 
      WHERE username = @userName AND password IS NULL AND IsDeleted = 0 
     END 

    ELSE 
     BEGIN 
      SELECT * FROM TblP 
      WHERE username = @userName AND password = @password AND IsDeleted = 0 
    END 
END 

GO 

我想查詢單表示相結合。不想要if條件。

Answer 1

CREATE PROCEDURE [dbo].[Pro_TblP] 
(
@userName varchar(100), 
@password varchar(100) 
) 
AS 
BEGIN 
    SELECT * FROM TblP 
    WHERE username = @userName AND COALESCE(password,'') = @password AND IsDeleted = 0 

END 

GO 

SQL Fiddle

Answer 2

試試下面的代碼： 時@Password爲空字符串或NULL將返回所有值。當你在@password變量中傳遞一個字符串時，它會過濾它。

CREATE PROCEDURE [dbo].[Pro_TblP] 
(
@userName varchar(100), 
@password varchar(100) 
) 
AS 
BEGIN 
    SELECT * FROM TblP 
     WHERE username = @userName AND IsDeleted = 0 
     And (password = @password OR isnull(@password,'') = '')   

END 

Answer 3

試試這個

alter PROCEDURE [dbo].[Pro_TblP] 
(
@userName varchar(100), 
@password varchar(100)='' 
) 
AS 
BEGIN 
    BEGIN 
     SELECT * FROM TblP 
     WHERE username = @userName AND IsNull(password,'')=@password AND IsDeleted = 0 
    END 
END 

Answer 4

SELECT * 
FROM TblP 
WHERE username = @userName AND 
     IsDeleted = 0 AND 
     (
     password = @password OR 
     password IS NULL AND @password = '' 
    )