mysql ON DUPLICATE KEY UPDATE
# 更新（保留）为原值（反引号），即如果原值是0，那么执行后是0
INSERT INTO user_admin_t (_id, `password`)
VALUES
('1','111') ,
('2','222')
ON DUPLICATE KEY UPDATE
`password` = `password`;
# 更新为字符串password，，即如果原值是0，那么执行后是字符串'password'
INSERT INTO user_admin_t (_id, `password`)
VALUES
('1','111') ,
('2','222')
ON DUPLICATE KEY UPDATE
`password` = 'password';
# 更新为新insert的值，即如果原值是0，那么执行后是111
INSERT INTO user_admin_t (_id, `password`)
VALUES
('1','111') ,
('2','222')
ON DUPLICATE KEY UPDATE
`password` = VALUES(`password`);
# 语法报错
INSERT INTO user_admin_t (_id, `password`)
VALUES
('1','111') ,
('2','222')
ON DUPLICATE KEY UPDATE
`password` = VALUES('password');
