mysql - INSERT INTO...ON DUPLICATE KEY UPDATE 增量语法

Question

我正在尝试将一个值从一个表递增到另一个表，但我无法找出正确的语法。有人可以帮我形成正确的陈述吗？提前致谢:

当前语句:

INSERT INTO points_1_day (nick, amount) 
(SELECT nick, SUM(amount) as increment 
FROM points_log 
WHERE dt >= NOW()-INTERVAL 1 day GROUP BY nick) 
ON DUPLICATE KEY UPDATE 
points_1_day.amount=points_1_day.amount+points_log.increment;

我收到此错误消息:

ERROR 1054 (42S22): Unknown column 'points_log.increment' in 'field list'

Answer 1

ON UPDATE 子句中的表达式不能引用 SELECT 中的列。

但他们可以引用 VALUES(amount) 来获取您尝试插入给定行的值。

INSERT INTO points_1_day (nick, amount) 
(SELECT nick, SUM(amount) as increment 
FROM points_log 
WHERE dt >= NOW()-INTERVAL 1 day GROUP BY nick) 
ON DUPLICATE KEY UPDATE 
points_1_day.amount=points_1_day.amount+VALUES(amount);

让我测试一下，看看它是否有效...

mysql> insert into points_1_day values (123, 10);
Query OK, 1 row affected (0.01 sec)

mysql> insert into points_log (nick, amount, dt) values (123, 15, NOW());
Query OK, 1 row affected (0.13 sec)

mysql> select * from points_1_day;
+------+--------+
| nick | amount |
+------+--------+
|  123 |     10 |
+------+--------+
1 row in set (0.00 sec)

mysql> INSERT INTO points_1_day (nick, amount)  (SELECT nick, SUM(amount) as increment  
    FROM points_log  WHERE dt >= NOW()-INTERVAL 1 day GROUP BY nick)  
    ON DUPLICATE KEY UPDATE  points_1_day.amount=points_1_day.amount+values(amount);
Query OK, 2 rows affected (0.02 sec)
Records: 1  Duplicates: 1  Warnings: 0

mysql> select * from points_1_day;
+------+--------+
| nick | amount |
+------+--------+
|  123 |     25 |
+------+--------+
1 row in set (0.00 sec)

mysql> INSERT INTO points_1_day (nick, amount)  (SELECT nick, SUM(amount) as increment  
    FROM points_log  WHERE dt >= NOW()-INTERVAL 1 day GROUP BY nick)  
    ON DUPLICATE KEY UPDATE  points_1_day.amount=points_1_day.amount+values(amount);
Query OK, 2 rows affected (0.00 sec)
Records: 1  Duplicates: 1  Warnings: 0

mysql> select * from points_1_day;
+------+--------+
| nick | amount |
+------+--------+
|  123 |     40 |
+------+--------+

是的，它似乎有效。

---

解释:http://dev.mysql.com/doc/refman/5.6/en/insert-on-duplicate.html说:

You can use the VALUES(col_name) function in the UPDATE clause to refer to column values from the INSERT portion of the INSERT ... ON DUPLICATE KEY UPDATE statement. In other words, VALUES(col_name) in the ON DUPLICATE KEY UPDATE clause refers to the value of col_name that would be inserted, had no duplicate-key conflict occurred. This function is especially useful in multiple-row inserts. The VALUES() function is meaningful only in INSERT ... UPDATE statements and returns NULL otherwise. Example:

INSERT INTO table (a,b,c) VALUES (1,2,3),(4,5,6)
  ON DUPLICATE KEY UPDATE c=VALUES(a)+VALUES(b);

这也适用于 INSERT...SELECT。但是 VALUES() 的参数是您要插入的列名，而不是 SELECT 中相应列的名称。