Full Outer join in SQL

About Outer Join in SQL

In this article, we will learn about outer join in SQL.
Outer Join between two tables helps to retrieve data that will be common to both the tables along with the unmatched data between the tables and thus helps to collect complete data from both the tables.

 

Outer Join in SQL

Full Outer  Join in SQL

In this article, we will learn about Full Outer Join in SQL.

Join enables data merging from tables. Is used to query data from multiple tables.
A full join is viewed as a result of union operation of an inner join, left join, and right join.

Outer Join in SQL

Full join Mechanism

  • It Returns all matched records i.e where the join condition is satisfied on both tables
  • It Returns all rows from right side table (unmatched right side rows)
  • It Returns all rows from the left side table(unmatched left side rows)
  • This join returns null values in place of nonmatching tuples in another table

Syntax

select col1,col2.... 
from 
tab1 
FULL JOIN 
tab2 
on tab1.colname=tab2.colname
  • 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 outer join SQL query

select ename,sal,d.deptno,dname,loc
from 
emp e 
FULL join
dept d
on e.deptno=d.deptno;
o/p
ROWNUM ENAME SAL DEPTNO DNAME LOC
1 KING 5000 10 ACCOUNTING NEW YORK
2 BLAKE 2850 30 SALES CHICAGO
3 CLARK 2450 10 ACCOUNTING NEW YORK
4 JONES 2975 20 RESEARCH DALLAS
5 SCOTT 3000 20 RESEARCH DALLAS
6 FORD 3000 20 RESEARCH DALLAS
7 SMITH 800 20 RESEARCH DALLAS
8 ALLEN 1600 30 SALES CHICAGO
9 WARD 1250 30 SALES CHICAGO
10 MARTIN 1250 30 SALES CHICAGO
11 TURNER 1500 30 SALES CHICAGO
12 ADAMS 1100 20 RESEARCH DALLAS
13 JAMES 950 30 SALES CHICAGO
14 MILLER 1300 10 ACCOUNTING NEW YORK
15 40 OPERATIONS BOSTON
14 records are matched with the join condition and remaining one record deptno=40 ,will not have any match from emp table hence it is appended with null values.

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