Sunday 24 June 2018

JOINs

The JOIN is used to combine rows from two or more tables.

SQL Inner Join :-

Select all rows from tables for the match between the columns in tables.
Same as JOIN

Syntax :-
SELECT column FROM table1
INNER JOIN table2
on table1.column = table2.column;

[only matching rows are retrieved]

 Example :-

SELECT emp.eno, emp.ename, dept.dno, dept.dname FROM emp
INNER JOIN dept
on emp.dno = dept.dno; 



SQL LEFT JOIN :-

Returns all rows from the left table, with the matching rows in the right table.
The result is NULL in the right side when there is no match.

Syntax :-

SELECT Columns FROM table1
LEFT [OUTER] JOIN table2
on table1.column = table2.column;
 
Example :-
SELECT emp.eno, emp.ename,dept.dno, dept.dname FROM emp
LEFT JOIN dept
on emp dno = dept.dno; 


SQL RIGHT JOIN :-

Returns all rows from the right table, with the matching rows in the left table.
The result is NULL in the left side when there is no match.

Syntax :-

SELECT columns FROM table1
RIGHT [OUTER] JOIN table2
on table1.column = table2.column;

Example :-


 FULL OUTER JOIN

Returns all rows from the left table and from the right table.
The combines the result of both LEFT and RIGHT joins.

Syntax :-

SELECT columns FROM table1
FULL [OUTER] JOIN table2
on table1.column = table2.column;

Example :-

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