如果literal不包含通配符,我为什么不能将isNull(col,literal)替换为col<>literal?

我遇到了一些旧代码,比如这个例子:

    DECLARE @tmpVal INT = 999

    DECLARE @tmpTable TABLE (col1 INT, col2 VARCHAR(20))

    INSERT INTO @tmpTable (col1, col2)
    VALUES 
        (1, 'Do not want this'),
        (2, 'Happy with this'),
        (3, NULL)

    SELECT
        col1,
        col2,
        -- I see code like this
        CASE
            WHEN ISNULL(col2, 'Do not want this') NOT LIKE 'Do not want this'
            THEN @tmpVal
        END                                                 AS CurrentCol,

        -- can I replace it with code like this because there is no else?
        CASE
            WHEN col2 <> 'Do not want this'
            THEN @tmpVal
        END                                                 AS BetterCol

    FROM 
        @tmpTable

我的想法是 ISNULL(col2, 'Do not want this') NOT LIKE 'Do not want this' 应替换为 col2 <> 'Do not want this' 因为它完美地处理了空的情况。

我可以使用BetterCol中的表单而不是CurrentCol中的表单作为when表达式,如果不是,为什么?有没有我看不到的边缘案例?