💼 Mainframe Interview Questions

INNER JOIN:

• Returns only matching rows from both tables
• If no match, row is excluded

LEFT OUTER JOIN:

• Returns all rows from left table
• Matching rows from right table
• NULL for right table if no match

-- INNER JOIN
SELECT E.NAME, D.DEPT_NAME
FROM EMPLOYEE E
INNER JOIN DEPARTMENT D
ON E.DEPT_ID = D.DEPT_ID;

-- LEFT OUTER JOIN
SELECT E.NAME, D.DEPT_NAME
FROM EMPLOYEE E
LEFT OUTER JOIN DEPARTMENT D
ON E.DEPT_ID = D.DEPT_ID;

Use LEFT JOIN when you want all employees even those without department.