MYSQL＆lt;＆gt;运算符而不是NOT IN

Question

如何使用<>代替NOT IN

来回答此问题

SELECT ward_no, COUNT(patient_id) AS occupying
FROM patient
WHERE ward_no NOT IN ('w5', 'w7')
GROUP BY ward_no

Answer 1

你可以这样做：

SELECT ward_no, COUNT(patient_id) AS occupying
FROM patient
WHERE ward_no <> 'w5' AND ward_no <> 'w7'
GROUP BY ward_no

但它比简单的NOT IN更重，所以我不会自己这样做。

Answer 2

使用此：

SELECT ward_no, COUNT(patient_id) AS occupying
FROM patient
WHERE ward_no <> 'w5' AND ward_no <> 'w7'
GROUP BY ward_no

Answer 3

从这里回答：https://dev.mysql.com/doc/refman/5.5/en/all-subqueries.html

NOT IN是＆lt;＆gt;的别名所有。因此，这两个陈述是相同的：

SELECT s1 FROM t1 WHERE s1 <> ALL (SELECT s1 FROM t2);
SELECT s1 FROM t1 WHERE s1 NOT IN (SELECT s1 FROM t2);