Question

我正在尝试运行以下语句：

INSERT into table (col1,col2,col3,col4)
    VALUES ('1','2','3','4') 
    ON DUPLICATE KEY UPDATE col3 = '3'

根据论坛中的许多示例，这应该适用于当前系统中的记录，但是当我执行此操作并在之后运行select时，col3不受影响。运行insert语句时没有错误。有什么想法吗？

Answer 1

见下文，在c3上创建了一个名为TAB的表，其中包含唯一键。

首先插入，它是一个光滑的插入物。
第二次插入时，c3的值更新为4，因为我在c3上有一个唯一的键。
第三次插入，它再次平滑，因为这次它的（1,2,3,4）不重复，因为该表只有（1,2,4,4）
第四次插入，被轰炸，因为插入值“3”是重复的，当尝试更新时，c3的更新值“4”也是重复的。

-

mysql> desc tab;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| c1    | int(11) | YES  |     | NULL    |       |
| c2    | int(11) | YES  |     | NULL    |       |
| c3    | int(11) | YES  | UNI | NULL    |       |
| c4    | int(11) | YES  |     | NULL    |       |
+-------+---------+------+-----+---------+-------+
4 rows in set (0.00 sec)

mysql> delete from tab;
Query OK, 2 rows affected (0.06 sec)

mysql> select * from tab;
Empty set (0.00 sec)

mysql> INSERT into tab (c1,c2,c3,c4)     VALUES ('1','2','3','4')      ON DUPLICATE KEY UPDATE c3 = '4';
Query OK, 1 row affected (0.05 sec)

mysql> select * from tab;
+------+------+------+------+
| c1   | c2   | c3   | c4   |
+------+------+------+------+
|    1 |    2 |    3 |    4 |
+------+------+------+------+
1 row in set (0.00 sec)

mysql> INSERT into tab (c1,c2,c3,c4)     VALUES ('1','2','3','4')      ON DUPLICATE KEY UPDATE c3 = '4';
Query OK, 2 rows affected (0.07 sec)

mysql> select * from tab;
+------+------+------+------+
| c1   | c2   | c3   | c4   |
+------+------+------+------+
|    1 |    2 |    4 |    4 |
+------+------+------+------+
1 row in set (0.00 sec)

mysql> INSERT into tab (c1,c2,c3,c4)     VALUES ('1','2','3','4')      ON DUPLICATE KEY UPDATE c3 = '4';
Query OK, 1 row affected (0.05 sec)

mysql> select * from tab;
+------+------+------+------+
| c1   | c2   | c3   | c4   |
+------+------+------+------+
|    1 |    2 |    4 |    4 |
|    1 |    2 |    3 |    4 |
+------+------+------+------+
2 rows in set (0.00 sec)

mysql> INSERT into tab (c1,c2,c3,c4)     VALUES ('1','2','3','4')      ON DUPLICATE KEY UPDATE c3 = '4';
ERROR 1062 (23000): Duplicate entry '4' for key 'c3_u'
mysql> select * from tab;
+------+------+------+------+
| c1   | c2   | c3   | c4   |
+------+------+------+------+
|    1 |    2 |    4 |    4 |
|    1 |    2 |    3 |    4 |
+------+------+------+------+
2 rows in set (0.00 sec)

MySQL重复更新不更新

1 个答案: