SQL Server CASE里面的where子句不适用于NULL值

Question

我想要的是什么时候@AddressCode是null然后只是执行

SELECT
    *
FROM
    Addresses
WHERE
    1= 1

如果@AddressCode不为NULL则执行

SELECT
    *
FROM
    Addresses
WHERE
    1= 1 AND @AddressCode=Addresses.AddressCode

我怎么能实现这个...我尝试了下面的查询,它不适用于NULL有价值的地址或什么时候@AddressCode is NULL....(地址只是一个虚构的表名)

Declare @AddressCode varchar(20)
Set @AddressCode=NULL

SELECT
    *
FROM
    Addresses
WHERE
    1= 1
    AND
    CASE @AddressCode
        WHEN NULL
        THEN Addresses.AddressCode
        ELSE @AddressCode
    END =Addresses.AddressCode

我努力但我无法做到...我知道我可以写IF语句并写个别选择语句但不想这样做,因为我有很多这样的标准@AddressCode:(

Answer 1

SELECT *
FROM
    Addresses
WHERE
    (@AddressCode IS NULL OR Addresses.AddressCode = @AddressCode)