在WHERE子句中使用可选参数

Question

我有一个SP

ALTER PROCEDURE dbo.sp_Compare
    @lst varchar(100),
    @frst varchar(100) = NULL,
    @passportNo varchar(50) = NULL
AS
SELECT * FROM dbo.User
WHERE LastName like '%' + @lst + '%'
    AND (
         FirstName like @frst + ' %'
         OR FirstName like '% ' + @frst + ' %'
         OR FirstName like '% ' + @frst
         OR FirstName = @frst
        )
    OR Passport = @passportNo;

有时@frs或@passportNo两者都可能无法获得详细信息

所以我想更改上面的查询,以便在未传递可选参数时(即,当其值为null时),不应考虑在该特定列上过滤该参数

即,如果@frst为NULL,则不应基于FirstName过滤结果,它应该像FirstName like '%' + @frst + '%'WHERE子句中没有条件一样工作.

如何在不为不同情况重复编写相同逻辑的情况下编写查询？

Answer 1

WHERE (@frst IS NULL OR 
    (
         LastName like '%' + @lst + '%'
         AND (
             FirstName like @frst + ' %'
             OR FirstName like '% ' + @frst + ' %'
             OR FirstName like '% ' + @frst
             OR FirstName = @frst
        )
    )
 )
 AND (@passportNo IS NULL OR
        Passport = @passportNo);

编辑:实际上这应该更有效:

WHERE ( @frst IS NULL OR FirstName like '%' + @frst + '%' )
AND   ( @lst  IS NULL OR LastName  like '%' + @lst  + '%' )
AND   ( @passportNo IS NULL OR Passport = @passportNo )