mysql 多字段更新

更新一個字段當好寫

update user set collect_num=(select sum(collect_num) from article where user_id=user.id) where user.id=1;
Query OK, 0 rows affected (17.36 sec)
Rows matched: 1 Changed: 0 Warnings: 0

 

問題是想更新多個字段
sql server 支持下面這種語法

update user set (article_num,collect_num,like_num)=(select count(*),sum(collect_num),sum(like_num) from article where user_id=user.id) where user.id=1;

 

試過並查官網后，發現mysql並不支持

先用最笨的辦法

update user set 
article_num=(select count(*) from article where user_id=user.id),
collect_num=(select sum(collect_num) from article where user_id=user.id),
like_num=(select sum(collect_num) from article where user_id=user.id) 
where user.id=1;
Query OK, 1 row affected (54.79 sec)
Rows matched: 1  Changed: 1  Warnings: 0

 

時間居然是更新一個字段的的3倍，可能是查了三次article表，驗證確實如此

mysql> explain select  (select count(*) from article where user_id=1),(select sum(collect_num) from article where user_id=1),(select sum(collect_num) from article where user_id=1);
+----+-------------+---------+-------+------------------------------+------------------------------+---------+------+---------+--------------------------+
| id | select_type | table   | type  | possible_keys                | key                          | key_len | ref  | rows    | Extra                    |
+----+-------------+---------+-------+------------------------------+------------------------------+---------+------+---------+--------------------------+
|  1 | PRIMARY     | NULL    | NULL  | NULL                         | NULL                         | NULL    | NULL |    NULL | No tables used           |
|  4 | SUBQUERY    | article | index | user_id_like_num_collect_num | user_id_like_num_collect_num | 104     | NULL | 3047331 | Using where; Using index |
|  3 | SUBQUERY    | article | index | user_id_like_num_collect_num | user_id_like_num_collect_num | 104     | NULL | 3047331 | Using where; Using index |
|  2 | SUBQUERY    | article | index | user_id_like_num_collect_num | user_id_like_num_collect_num | 104     | NULL | 3047331 | Using where; Using index |
+----+-------------+---------+-------+------------------------------+------------------------------+---------+------+---------+--------------------------+

 

不能忍

 

能想到的辦法就是起臨時表（或外部寫代碼，python什么的，實現類似臨時表的功能）了，畢竟臨時表萬能。

 

但還是想在sql層面解決

 

update user u 
JOIN (select user_id as user_id,count(*) as article_num,sum(collect_num) as collect_num,sum(like_num) as like_num from article where user_id=1) t 
on u.id=t.user_id 
set u.article_num=t.article_num,u.collect_num=t.collect_num,u.like_num=t.like_num 
where u.id=1;

 

雖然代碼不如sqlserver 漂亮，需要改兩個值，不過達到目的了，時間並不比單字段耗時。

 

更改為單查詢條件

update user u 
JOIN (select user_id as user_id,count(*) as article_num,sum(collect_num) as collect_num,sum(like_num) as like_num 
from article 
group by user_id) t
 on u.id=t.user_id  
set u.article_num=t.article_num,u.collect_num=t.collect_num,u.like_num=t.like_num  where u.id=101;

 

總算差不多了

個人最熟悉sqlserver,mysql只是順帶打醬油的，如果mysql有更有效的辦法，還望不吝告知。