在MySQL中为on duplicate key update添加约束
要添加约束,语法如下−
alter table yourTableName add constraint anyName unique(yourColumnName);
首先,让我们创建一个表 −
mysql> create table DemoTable1459
-> (
-> Name varchar(20),
-> Score int
-> );
Query OK, 0 rows affected (0.72 sec)
以下是为on duplicate key update添加约束的查询语句−
mysql> alter table DemoTable1459 add constraint Name_const unique(Name);
Query OK, 0 rows affected (1.09 sec)
Records: 0 Duplicates: 0 Warnings: 0
使用insert命令向表中插入一些记录−
mysql> insert into DemoTable1459 values('Chris',57) on duplicate key update Score=Score+10;
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable1459 values('David',89) on duplicate key update Score=Score+10;
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable1459 values('Chris',78) on duplicate key update Score=Score+10;
Query OK, 2 rows affected (0.33 sec)
使用select语句显示表中的所有记录−
mysql> select * from DemoTable1459;
将会产生以下输出−
+-------+-------+
| Name | Score |
+-------+-------+
| Chris | 67 |
| David | 89 |
+-------+-------+
2 rows in set (0.00 sec)
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