SQL: select * from table where id IN (3,6,9,1,2,5,8,7); 

这样的情况取出来后，其实，id还是按1,2,3,4,5,6,7,8,9,排序的，但如果我们真要按IN里面的顺序排序怎么办？SQL能不能完成？是否需要取回来后再foreach一下？其实mysql就有这个方法 

sql: select * from table where id IN (3,6,9,1,2,5,8,7) order by field(id,3,6,9,1,2,5,8,7); 

出来的顺序就是指定的顺序了。

MySQL中NOT IN语句对NULL值的处理 

mysql> SELECT COUNT(name) FROM CVE WHERE name NOT IN ('CVE-1999-0001', 'CVE-1999-0002'); 
+-------------+ 
| count(name) | 
+-------------+ 
| 17629 | 
+-------------+ 
1 row in set (0.02 sec) 
mysql> SELECT COUNT(name) FROM CVE WHERE name NOT IN ('CVE-1999-0001', 'CVE-1999-0002', NULL); 
+-------------+ 
| count(name) | 
+-------------+ 
| 0 | 
+-------------+ 
1 row in set (0.01 sec) 
当在子查询中出现NULL的时候，结果就一定是0了。查了一下手册，确实有这样的说法。所以最后实际采用了这样的查询： 
SELECT COUNT(DISTINCT name) 
FROM CVE 
WHERE name NOT IN (SELECT cveID FROM cve_sig WHERE cveID IS NOT NULL) 
顺便提一下MySQL中正则表达式匹配的简单使用： 
SELECT COUNT(alarmID) 
FROM Alarm 
WHERE (CVE NOT RLIKE '^CVE-[0-9]{4}-[0-9]{4}$' OR CVE IS NULL) 
当然，RLIKE也可以写作REGEXP，我个人倾向于使用RLIKE，因为拼写接近LIKE，可以见名知义。 

mysql - not in 
table:info primary key(id, info_type_id) 
id, info_type_id, programme_id, episode_id 
3, 4, 382, 100034 
3, 8, 382, 100034 
4, 8, 382, 100034 
6, 8, 382, 100034 
7, 8, 382, 100034 
8, 8, 382, 100034 
9, 8, 382, 100034 
10, 8, 382, 100034 
11, 8, 382, 100034 
12, 8, 382, 100034 
13, 8, 382, 100034 
100001, 4, 382, 100034 
100002, 4, 382, 100034 

排除(id=3 && info_type_id=8) and (id=4 && info_type_id=8)這兩條記錄，即找出其它記錄 
error: select * from info where episode_id=100034 and id not in(3,4) and info_type_id not in (8); 
error result: 
id, info_type_id, programme_id, episode_id 
100001, 4, 382, 100034 
100002, 4, 382, 100034 
correct: select * from info where episode_id=100034 and (id<>3 or info_type_id<>8) and (id<>4 or info_type_id<>8); 
correct result: 
id, info_type_id, programme_id, episode_id 
3, 4, 382, 100034 
6, 8, 382, 100034 
7, 8, 382, 100034 
8, 8, 382, 100034 
9, 8, 382, 100034 
10, 8, 382, 100034 
11, 8, 382, 100034 
12, 8, 382, 100034 
13, 8, 382, 100034 
100001, 4, 382, 100034 
100002, 4, 382, 100034 
理 解：id<>3 or info_type_id<>8排除掉id=3 && info_type_id=8這條記錄,當表中主鍵多于一個時，不能簡單地使用key1 NOT IN (……) AND key2 NOT IN (……) ..