DROP TABLE IF EXISTS stuInfo;
CREATE TABLE stuInfo (
id INT NOT NULL COMMENT '序号',
name VARCHAR(20) NOT NULL DEFAULT '' COMMENT '姓名',
age INT NOT NULL DEFAULT 0 COMMENT '年龄',
PRIMARY KEY (id),
UNIQUE KEY uniq_name(name)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='学生表';
在ON DUPLICATE KEY UPDATE后VALUES解释：
VAULES(age)指的是待插入的记录的值
age指得是表的自身值，已插入值。
（1）第一种情形：
#VALUES(age) 待插入值 25
INSERT INTO stuInfo (id,name,age) VALUES (1,'yoona',20),(1,'xiaosi',25) ON DUPLICATE KEY UPDATE age = VALUES(age) + 1;
INSERT INTO stuInfo (id,name,age) VALUES (1,'yoona',20);
UPDATE stuInfo
SET age = VALUES(age) + 1
WHERE id = 1;
运行结果：
mysql> INSERT INTO stuInfo (id,name,age) VALUES (1,'yoona',20),(1,'xiaosi',25) ON DUPLICATE KEY UPDATE age = VALUES(age) + 1;
Query OK, 3 rows affected (0.01 sec)
Records: 2 Duplicates: 1 Warnings: 0
mysql> select * from stuInfo;
+----+-------+-----+
| id | name | age |
+----+-------+-----+
| 1 | yoona | 26 |
+----+-------+-----+
1 row in set (0.00 sec)
（2）第二种情形：
#age 已插入值 20
INSERT INTO stuInfo (id,name,age) VALUES (1,'yoona',20),(1,'xiaosi',25) ON DUPLICATE KEY UPDATE age = age + 1;
INSERT INTO stuInfo (id,name,age) VALUES (1,'yoona',20);
UPDATE stuInfo
SET age = age + 1
WHERE id = 1;
运行结果：
mysql> INSERT INTO stuInfo (id,name,age) VALUES (1,'yoona',20),(1,'xiaosi',25) ON DUPLICATE KEY UPDATE age = age + 1;
Query OK, 3 rows affected (0.02 sec)
Records: 2 Duplicates: 1 Warnings: 0
mysql> select * from stuInfo;
+----+-------+-----+
| id | name | age |
+----+-------+-----+
| 1 | yoona | 21 |
+----+-------+-----+
1 row in set (0.00 sec)
