mysql技巧：如果记录存在则更新/如果不存在则插入的三种处理方法

CREATE TABLE `t_emp` (
  `f_id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键id',
  `f_emp_code` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT '' COMMENT '员工号',
  `f_emp_name` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT '' COMMENT '员工姓名',
  `f_city` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT '' COMMENT '所属城市',
  `f_salary` int(11) DEFAULT '1200' COMMENT '工资',
  `f_last_update_time` datetime(3) DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3) COMMENT '最后修改时间',
  PRIMARY KEY (`f_id`),
  UNIQUE KEY `idx_emp_code` (`f_emp_code`)
) ENGINE=InnoDB AUTO_INCREMENT=0 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci COMMENT='员工表'

INSERT INTO t_emp(
	f_emp_code ,
	f_emp_name ,
	f_city ,
	f_salary
) SELECT '10007' ,
	 '新人' ,
	 '西安' ,
	 1000 
	FROM DUAL WHERE NOT EXISTS(
	SELECT * FROM t_emp WHERE f_emp_code = '10007'
);

UPDATE t_emp SET f_emp_name = '新人2' ,
 f_city = '西安' ,
 f_salary = IF(1000 > f_salary , 1000 , f_salary) WHERE f_emp_code = '10007'

REPLACE INTO t_emp(
	f_emp_code ,
	f_emp_name ,
	f_city ,
	f_salary
) VALUES(
	'10007' ,
	'新人' ,
	'西安' ,
	IF(1000 > f_salary , 1000 , f_salary));

INSERT INTO t_emp(
	f_emp_code ,
	f_emp_name ,
	f_city ,
	f_salary)
VALUES(
	'10007' ,
	'新人' ,
	'西安' ,
	1000) 
ON DUPLICATE KEY UPDATE 
	f_emp_code = values(f_emp_code) ,
	f_emp_name = values(f_emp_name),
	f_city = values(f_city),
	f_salary = if(values(f_salary)>f_salary,values(f_salary),f_salary);