SELECT e.ename, e.empno
FROM emp e;
SELECT e.ename, d.dname
FROM emp e
JOIN dept d ON e.deptno = d.deptno
WHERE e.job = 'CLERK';
SELECT e.ename, d.dname
FROM emp e
JOIN dept d ON e.deptno = d.deptno
WHERE e.sal >= 2600;
SELECT e.ename, e.sal, s.grade
FROM emp e
JOIN salgrade s ON e.sal BETWEEN s.losal AND s.hisal;
SELECT e.sal AS emp_sal,
m.sal AS mgr_sal
FROM emp e
LEFT JOIN emp m ON e.mgr = m.empno;
SELECT e.empno,
m.empno AS mgr_empno
FROM emp e
LEFT JOIN emp m ON e.mgr = m.empno;
SELECT e.ename,
d.dname
FROM dept d
LEFT JOIN emp e ON d.deptno = e.deptno;
SELECT e.empno, d.deptno, d.loc
FROM emp e
JOIN dept d ON e.deptno = d.deptno
WHERE d.deptno = 20;