将查询中的空字符串考虑为null

Question

我正在使用sql server R2 。 我有一个存储过程，我在其中传递了两个参数，分别为@username varchar(100)和@password varchar(100) 。

现在，当我第一次从应用程序创建用户时，密码将为NULL。

我想查询返回匹配用户名和密码的记录。 问题是代码将empty string传递给stored procedure 。 我想要一些考虑或自动将empty string to NULL转换empty string to NULL东西。 我已经有了使用if condition解决方案，但是我想使用单个查询，而不是if条件。

编辑：

它是一个简单的存储过程：

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

我想以单一表示形式组合查询。 不需要if条件。

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小提琴

Answer 2

尝试下面的代码：@password为空字符串或null时，它将返回所有值。 当您在@password变量中传递字符串时，它将对其进行过滤。

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

尝试这个

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 = ''
      )