SQL查询结果错误

Question

我有一个视图（A），在运行以下查询时包含9行：

SELECT *
FROM A
WHERE card_num_full is null OR card_num_full LIKE ''

表B不包含这9行，那么为什么在运行以下查询时，我仍然得到9行？

SELECT *
FROM A
WHERE card_num_full is null OR card_num_full LIKE ''
      AND field_1 IN   
        (SELECT field_1
         FROM B)

Answer 1

为or

括起来

SELECT * 
FROM A 
WHERE (card_num_full is null 
    or card_num_full like '')
and field_1 in (select field_1 from B)

Answer 2

您可以使用ISNULL()功能，但不需要括号。

SELECT * 
FROM A WHERE isnull(card_num_full,'') like ''  
    and field_1 in
        (select field_1 from B)