在 MySQL 中实现 INSERT ... ON DUPLICATE KEY UPDATE
mysqlmysqli database
INSERT ... ON DUPLICATE KEY UPDATE 的工作方式是，如果发现重复的唯一键或主键，它将执行 UPDATE。仅当出现重复值时才执行 UPDATE。
首先我们创建一个表 −
mysql> create table DemoTable733 ( StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, StudentName varchar(100), StudentMarks int, UNIQUE KEY Un_Name (StudentName) ); Query OK, 0 rows affected (0.60 sec)
使用 insert 命令在表中插入一些记录 −
mysql> insert into DemoTable733(StudentName,StudentMarks) values('John',45)
ON DUPLICATE KEY UPDATE StudentMarks=86;
Query OK, 1 row affected (0.19 sec)
mysql> insert into DemoTable733(StudentName,StudentMarks) values('Adam',65)
ON DUPLICATE KEY UPDATE StudentMarks=86;
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable733(StudentName,StudentMarks) values('Carol',75)
ON DUPLICATE KEY UPDATE StudentMarks=86;
Query OK, 1 row affected (0.08 sec)
mysql> insert into DemoTable733(StudentName,StudentMarks) values('John',45)
ON DUPLICATE KEY UPDATE StudentMarks=86;
Query OK, 2 rows affected (0.12 sec)
使用 select 语句显示表中的所有记录 −
mysql> select *from DemoTable733;
这将产生以下输出 -
+-----------+-------------+--------------+ | StudentId | StudentName | StudentMarks | +-----------+-------------+--------------+ | 1 | John | 86 | | 2 | Adam | 65 | | 3 | Carol | 75 | +-----------+-------------+--------------+ 3 rows in set (0.00 sec)
