MYSQL <>運算符代替NOT IN

Question

我怎樣才能讓這個答案通過<>代替NOT IN

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

Answer 1

你可以這樣做：

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

但它不是一個簡單的NOT方式較重IN，所以我不會那樣做。

Answer 2

使用此：從這裏

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

Answer 3

答：https://dev.mysql.com/doc/refman/5.5/en/all-subqueries.html

NOT IN是<別名> ALL。因此，這兩個語句是相同的：

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