Difference between UNION, MINUS and INTERSECT
The union uses to combine the result of two or more tables from the select statements. The union select statement should select the same number of fields in the result set. The UNION operator returns only distinct rows that appear in either result. The UNION ALL operator returns all rows from two result sets. The UNION ALL operator does not eliminate duplicate.
MINUS takes the first result set, and removes any that exist in the second result set; it also removes any duplicates.
The intersect return the results from two or more select statements.
-- UNION SELECT * FROM HR.employees WHERE DEPARTMENT_ID = 90 UNION SELECT * FROM HR.employees WHERE DEPARTMENT_ID = 60; -- MINUS SELECT * FROM HR.employees MINUS SELECT * FROM HR.employees WHERE DEPARTMENT_ID >= 60; -- INTERSECT SELECT * FROM HR.employees WHERE EMPLOYEE_ID IN (100, 103, 105) INTERSECT SELECT * FROM HR.employees WHERE EMPLOYEE_ID in (100, 102, 104, 105)