在 MySQL 中添加对重复键更新的约束
mysqlmysqli database更新于 2024/2/12 15:18:00
要添加约束，语法如下 −
alter table yourTableName add constraint anyName unique(yourColumnName);
首先我们创建一个表 −
mysql> create table DemoTable1459 -> ( -> Name varchar(20), -> Score int -> ); Query OK, 0 rows affected (0.72 sec)
以下是添加对重复键更新的约束的查询 −
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 插入命令在表中插入一些记录 −
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;
这将产生以下输出 −
+-------+-------+ | Name | Score | +-------+-------+ | Chris | 67 | | David | 89 | +-------+-------+ 2 rows in set (0.00 sec)
