SQL Joins are to combine data from different tables to show relation between them . Example you can join EMP table with DEPT table to get department along with Employee records.
See Also : Learn about Oracle Architecture here
There are basically below type of Joins :
1. INNER Join :
SELECT emp.empno, emp.ename ,emp.job, dept.deptno,dept.dname
FROM emp
INNER JOIN dept
ON emp.deptno= dept.deptno;
FROM emp
INNER JOIN dept
ON emp.deptno= dept.deptno;
2. Left Outer Join :
SELECT emp.empno, emp.ename ,emp.job, dept.deptno,dept.dname
FROM emp
LEFT OUTER JOIN dept
ON emp.deptno= dept.deptno;
FROM emp
LEFT OUTER JOIN dept
ON emp.deptno= dept.deptno;
3. Right Outer Join
SELECT emp.empno, emp.ename ,emp.job, dept.deptno,dept.dname
FROM emp
RIGHT OUTER JOIN dept
ON emp.deptno= dept.deptno;
FROM emp
RIGHT OUTER JOIN dept
ON emp.deptno= dept.deptno;
4. Full Outer Join
SELECT emp.empno, emp.ename ,emp.job, dept.deptno,dept.dname
FROM emp
FULL OUTER JOIN dept
ON emp.deptno= dept.deptno;
FROM emp
FULL OUTER JOIN dept
ON emp.deptno= dept.deptno;
I Found a good article on "Type of Oracle join with Example" here.
See Also : Learn about Oracle Architecture here
Hope you enjoyed this small and useful article on SQL joins in Oracle :)
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