用Select插入MySQL

Question

I have two tables named employees and testdept .In employees table there are two fields as employee_id and department . testdept table contains two fields as epfno and deptid .

Now what I want to do is insert those id's from testdept table to employees table department field where employee_id matches with the epfno.

I have tried with the below code. It inserts the data as a new row. That is the problem.

INSERT INTO employees (department)
SELECT t.deptid
FROM  testdept t, employees e
WHERE  t.epfno = e.employee_id

Answer 1

If I understood you correctly, you want an UPDATE statement and not an INSERT :

UPDATE employees e
JOIN testdept t
 ON(e.employee_id = t.epfno)
SET e.department = t.deptid

This will update the records in employee table with the data from the corresponding row in testdept table