Need to find the employees who have switched jobs atleast twice I am trying the following query on the tables which are described below:



SELECT * FROM job_history INNER JOIN employees
ON job_history.employee_id = employees.employee_id
WHERE employee_ID IN
    (SELECT employee_id FROM

        (SELECT employee_id, COUNT(employee_id) AS cnt
         FROM job_history
         GROUP BY employee_id
         HAVING cnt >= 2) INNER
    )    
    OUTER;



But I get an error in MySQL, that every derived table must have its own alias

We have a table job_history(employee_id, start_date, end_date, job_id, department_id) containing the following data:



'102', '1993-01-13', '1998-06-24', 'IT_PROG', '60'
'101', '1989-09-21', '1993-10-27', 'AC_ACCOUNT', '110'
'101', '1993-10-28', '1997-03-15', 'AC_MGR', '110'
'201', '1996-02-17', '1999-12-19', 'MK_REP', '20'
'114', '1998-03-24', '1999-12-31', 'ST_CLERK', '50'
'122', '1999-01-01', '1999-12-31', 'ST_CLERK', '50'
'200', '1987-09-17', '1993-06-17', 'AD_ASST', '90'
'176', '1998-03-24', '1998-12-31', 'SA_REP', '80'
'176', '1999-01-01', '1999-12-31', 'SA_MAN', '80'
'200', '1994-07-01', '1998-12-31', 'AC_ACCOUNT', '90'


We have another table employees(employee_id int,
first_name varchar(20),
last_name varchar(25) not null,
email varchar(25) not null,
phone_number varchar(20),
hire_date date not null,
job_id varchar(10) not null,
salary float,
commission_pct float,
manager_id int,
department_id int,
constraint emp_pk primary key(employee_id)
)
Your Query should be like:

SELECT * FROM job_history INNER JOIN employees 
ON job_history.employee_id = employees.employee_id
WHERE job_history.employee_ID IN
    (SELECT employee_id
         FROM job_history
         GROUP BY employee_id
         HAVING COUNT(employee_id) &gt;= 2
    );


so you missed the alias before the id "WHERE job_history.employee_ID IN..", and the where in change it to what above...