Outer Join

Full Outer Join in DBMS

A join is a query that combines rows from two or more tables, views or materialized views

Definition: Full join returns all the matched records and unmatched records from both left side table and right side table

A Full join is viewed as a union of an inner join, left outer join and right outer join

How full join works

  • It Returns all the records that are matched based upon the condition (inner join)
  • It Returns all the unmatched records from the right table (right outer)
  • It Returns all the unmatched record from the left table (left outer)
  • It places normal values on unmatched records when there is no data to be appended for some tuples
Full Join outer join in DBMS

Syntax:

select 
col1,col2,col3.... 
from  
FULL JOIN table2
on
.commoncolname>=name> Consider two tables Emp table
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
7839 KING PRESIDENT 17-NOV-81 5000 10
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7566 JONES MANAGER 7839 02-APR-81 2975 20
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7934 MILLER CLERK 7782 23-JAN-82 1300 10
Dept table
DEPTNO DNAME LOC
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON

Full Join SQL query

select rownum,Empno,Ename,Emp.Deptno,Dname, sal*12 annsal,loc,job
from 
Emp
FULL JOIN
Dept
on Emp.Deptno=Dept.deptno and dname='SALES';
O/P
ROWNUM EMPNO ENAME DEPTNO DNAME ANNSAL LOC JOB
1 7839 KING 10 60000 PRESIDENT
2 7698 BLAKE 30 SALES 34200 CHICAGO MANAGER
3 7782 CLARK 10 29400 MANAGER
4 7566 JONES 20 35700 MANAGER
5 7788 SCOTT 20 36000 ANALYST
6 7902 FORD 20 36000 ANALYST
7 7369 SMITH 20 9600 CLERK
8 7499 ALLEN 30 SALES 19200 CHICAGO SALESMAN
9 7521 WARD 30 SALES 15000 CHICAGO SALESMAN
10 7654 MARTIN 30 SALES 15000 CHICAGO SALESMAN
11 7844 TURNER 30 SALES 18000 CHICAGO SALESMAN
12 7876 ADAMS 20 13200 CLERK
13 7900 JAMES 30 SALES 11400 CHICAGO CLERK
14 7934 MILLER 10 15600 CLERK
15 OPERATIONS BOSTON
16 ACCOUNTING NEW YORK
17 RESEARCH DALLAS
  • There are 6 matched records with deptno=30 and name =’SALES’ from dept table with emp table and 3 records from right side table ‘dept’ are unmatched are displayed ,if there is no data to be added on unmatched records null values are added and 9 unmatched records from left side table with null values when there is no data to be appended for tuples
  • 6(inner join matched records)+9(unmatched records from the left table)+3(unmatched records from the right table)=17 records (full outer join )