如何使用变量或未知数量的参数编写 tsql 搜索函数？

Question

所以我正在尝试编写一个 t-sql 函数，该函数将在数据库中搜索某些字段，但前提是这些字段不为空。因此，在下面的查询中，我的 c# 调用将传入这些参数，但如果我不想传入其中一个参数或其中一个为空，我希望它仍然搜索，但只能通过“ t null（基本上从 where 子句中排除）。是否有捷径可寻？还是我必须对每种输入组合进行单独查询？

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

你可以跳过null的过滤器

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)
)

Answer 2

这将允许忽略设置为 NULL 的参数。

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