删除emp_no重复的记录，只保留最小的id对应的记录。_牛客题霸

删除emp_no重复的记录，只保留最小的id对应的记录。 CREATE TABLE IF NOT EXISTS titles_test ( id int(11) not null primary key, emp_no int(11) NOT NULL, title varchar(50) NOT NULL, from_date date NOT NULL, to_date date DEFAULT NULL); insert into titles_test values ('1', '10001', 'Senior Engineer', '1986-06-26', '9999-01-01'), ('2', '10002', 'Staff', '1996-08-03', '9999-01-01'), ('3', '10003', 'Senior Engineer', '1995-12-03', '9999-01-01'), ('4', '10004', 'Senior Engineer', '1995-12-03', '9999-01-01'), ('5', '10001', 'Senior Engineer', '1986-06-26', '9999-01-01'), ('6', '10002', 'Staff', '1996-08-03', '9999-01-01'), ('7', '10003', 'Senior Engineer', '1995-12-03', '9999-01-01'); 删除后titles_test表为(注：最后会select * from titles_test表来对比结果) id emp_no title from_date to_date 1 10001 Senior Engineer 1986-06-26 9999-01-01 2 10002 Staff 1996-08-03 9999-01-01 3 10003 Senior Engineer 1995-12-03 9999-01-01 4 10004 Senior Engineer 1995-12-03 9999-01-01

示例1

输入

drop table if exists titles_test;
CREATE TABLE titles_test (
   id int(11) not null primary key,
   emp_no  int(11) NOT NULL,
   title  varchar(50) NOT NULL,
   from_date  date NOT NULL,
   to_date  date DEFAULT NULL);

insert into titles_test values
('1', '10001', 'Senior Engineer', '1986-06-26', '9999-01-01'),
('2', '10002', 'Staff', '1996-08-03', '9999-01-01'),
('3', '10003', 'Senior Engineer', '1995-12-03', '9999-01-01'),
('4', '10004', 'Senior Engineer', '1995-12-03', '9999-01-01'),
('5', '10001', 'Senior Engineer', '1986-06-26', '9999-01-01'),
('6', '10002', 'Staff', '1996-08-03', '9999-01-01'),
('7', '10003', 'Senior Engineer', '1995-12-03', '9999-01-01');

输出

1|10001|Senior Engineer|1986-06-26|9999-01-01
2|10002|Staff|1996-08-03|9999-01-01
3|10003|Senior Engineer|1995-12-03|9999-01-01
4|10004|Senior Engineer|1995-12-03|9999-01-01