Detect Duplicate entries in table by composite key

table TABLE_NAME has key1 , key2 , key3 columns .


select key1,key2, key3 from TABLE_NAME group by key1, key2 , key3 having count(*)>1

Copy column from one table to other table

------------------------
EMPLOYEE TABLE
------------------------
salCodeid name
------------------------



---------------------------------------------
SALARY TABLE
----------------------------------------------
idsalCode salary basic tax bonus
---------------------------------------------



Column exists in target table then

INSERT INTO EMPLOYEE (salCodeid) SELECT idsalCode FROM SALARY

If column does not exixts

ALTER EMPLOYEE (salCodeid) SELECT idsalCode FROM SALARY