有一个员工employees表简况如下:

对应SQL语句:

drop table if exists  `employees` ; 
CREATE TABLE `employees` (
`emp_no` int(11) NOT NULL,
`birth_date` date NOT NULL,
`first_name` varchar(14) NOT NULL,
`last_name` varchar(16) NOT NULL,
`gender` char(1) NOT NULL,
`hire_date` date NOT NULL,
PRIMARY KEY (`emp_no`));

INSERT INTO employees VALUES(10001,'1953-09-02','Georgi','Facello','M','1986-06-26');
INSERT INTO employees VALUES(10002,'1964-06-02','Bezalel','Simmel','F','1985-11-21');
INSERT INTO employees VALUES(10003,'1959-12-03','Parto','Bamford','M','1986-08-28');
INSERT INTO employees VALUES(10004,'1954-05-01','Chirstian','Koblick','M','1986-12-01');
INSERT INTO employees VALUES(10005,'1955-01-21','Kyoichi','Maliniak','M','1989-09-12');
INSERT INTO employees VALUES(10006,'1953-04-20','Anneke','Preusig','F','1989-06-02');
INSERT INTO employees VALUES(10007,'1957-05-23','Tzvetan','Zielinski','F','1989-02-10');
INSERT INTO employees VALUES(10008,'1958-02-19','Saniya','Kalloufi','M','1994-09-15');
INSERT INTO employees VALUES(10009,'1952-04-19','Sumant','Peac','F','1985-02-18');
INSERT INTO employees VALUES(10010,'1963-06-01','Duangkaew','Piveteau','F','1989-08-24');
INSERT INTO employees VALUES(10011,'1953-11-07','Mary','Sluis','F','1990-01-22');

解题思路：

1. 首先此题是查询入职日期倒数第三的日期。
2. 根据日期需要去插入对应，这一天入职的所有员工的信息。
3. 此题容易忽略同一天入职日期存在多个，例如2019-06-05存在多个，这时候倒数第三或许就是不真实的倒数第三的日期。因此在查询的时候，需要考虑。可以使用group对日期做一个分组，也可以使用district对日期进行去重，得到的日期就是唯一的。
4. 根据得到的日期，作为一个临时表，作为查询所有员工的信息。

答案

使用distinct进行排重查询。

SELECT
    *
FROM
    employees
WHERE
    hire_date = ( SELECT DISTINCT hire_date FROM employees ORDER BY hire_date DESC LIMIT 2, 1 );

使用group对日期去重查询。

SELECT
    *
FROM
    employees
WHERE
    hire_date = ( SELECT hire_date FROM employees GROUP BY hire_date ORDER BY hire_date DESC LIMIT 2, 1 );