运行以下查询时，我有一个包含9行的视图（A）：
SELECT *
FROM A
WHERE card_num_full is null OR card_num_full LIKE ''
表B不包含这9行，所以为什么在运行以下查询时仍然得到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)
用括号括住 or
SELECT *
FROM A
WHERE (card_num_full is null
or card_num_full like '')
and field_1 in (select field_1 from B)
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