如何用變量或未知數量的參數編寫tsql搜索函數？

Question

因此，我試圖編寫一個t-sql函數，它將搜索數據庫中的某些字段，但前提是字段不爲空。所以在下面的查詢中，我的c＃調用會傳入這些參數，但是如果我不想傳入其中一個參數或者其中一個參數爲null，我希望它仍然可以搜索，但只能通過不是' t null（基本上從where子句中排除）。是否有捷徑可尋？或者我將不得不爲每個輸入組合單獨查詢？

CREATE FUNCTION [dbo].[Search] 
(
    @firstname VarChar(50), 
    @lastname VarChar(80), 
    @userId VarChar(50), 
    @vehicle VarChar(50) 
) 
RETURNS @returntable TABLE 
(
    firstname VarChar(50), 
    lastname VarChar(80), 
    userId VarChar(50), 
    vehicle VarChar(50), 
    passengers VarChar(50) 
) 
AS 
BEGIN 
    INSERT @returntable 
    SELECT * FROM Drivers 
    Where firstname = @firstname and lastname = @lastname and 
      userid = @userId and vehicle = @vehicle 
RETURN 
END 

Answer 1

這將允許忽略設置爲NULL的參數。

CREATE FUNCTION [dbo].[Search] 
(
    @firstname VarChar(50), 
    @lastname VarChar(80), 
    @userId VarChar(50), 
    @vehicle VarChar(50) 
) 
RETURNS @returntable TABLE 
(
    firstname VarChar(50), 
    lastname VarChar(80), 
    userId VarChar(50), 
    vehicle VarChar(50), 
    passengers VarChar(50) 
) 
AS 
BEGIN 
    INSERT @returntable 
    SELECT * FROM Drivers 
    Where (@firstname IS NULL OR firstname = @firstname) AND 
      (@lastname IS NULL OR lastname = @lastname) AND 
      (@userId IS NULL OR userid = @userId) AND 
      (@vehicle IS NULL OR vehicle = @vehicle) 
RETURN 
END 

Answer 2

可以跳過濾波器，是null

CREATE FUNCTION [dbo].[Search] 
( 
    @firstname VarChar(50), 
    @lastname VarChar(80), 
    @userId VarChar(50), 
    @vehicle VarChar(50) 
) 
RETURNS TABLE 
AS 
RETURN 
(
    SELECT * FROM Drivers 
    Where 
    (@firstname is null or firstname = @firstname) 
    and (@lastname is null or lastname = @lastname) 
    and (@userId is null or userid = @userId) 
    and (@vehicle is null or vehicle = @vehicle) 
)