Sql joins

SQL JOINS
PRESENTED BY
Siddhesh S. Palkar

WHAT IS JOINNING ???
Introduction

 A SQL join clause combines columns from
one or more tables in a relational
database. It creates a set that can be
saved as a table or used as it is.
 A JOIN is a means for combining columns
from one or more tables by using values
common to each.

Type of SQL Joins
Inner Join
Outer Join
Cross Join

Inner Joins
Inner join returns only those records that match in both the tables.
Syntax:
Select * from table 1 INNER JOIN
table 2
ON
Table 1.Column 1=table 2.Column 1

Scenario
EmpID EmpName DepID
1 Siddhesh 3
2 Sumit 4
3 Rakesh 1
4 Omkar 2
5 Shailesh 4
DepID DepName
1 Accounts
2 Sales
3 HR
4 Technical
Tab_Employee Tab_Department

Inner Join ( Example )
Query :
SELECT a.EmpID , a.EmpName , Tab_Department.DepName
FROM Tab_Employee a
INNER JOIN Tab_Department b
ON a.DepID = b.DepID;
Result :
EmpID EmpName DepName
1 Siddhesh HR
2 Sumit Technical
3 Rakesh Accounts
4 Omkar Sales
5 Shailesh Technical

Outer Joins
There are three types of Outer Joins :
 Left Outer Joins
 Right Outer Joins
 Full Outer Joins

Left Outer Joins
Left outer join returns all records/rows from left table and from right table
returns only matched records.
Syntax:
Select * from Table 1
Left Outer Join Table 2
ON
Table 1.Column 1=Table 2.Column 1

Right Outer Joins
Syntax:
Right Outer Join Table 2
ON
Right outer join returns all records/rows from right table and from left table
returns only matched records.

Full Outer Joins
Full outer join combines left outer join and right outer join. This join returns
all records/rows from both the tables.
Syntax:
Full Outer Join Table 2
ON

Scenario
EmpID EmpName DepID
1 Siddhesh 3
2 Sumit 4
3 Rakesh 1
4 Omkar 2
5 Shailesh 4
DepID EmpName
1 Accounts
2 Sales
3 HR
4 Technical

Left Outer Join ( Example )
Query :
SELECT a.DepID , a.DepName , b.EmpID , b.EmpName
FROM Tab_Department a
LEFT OUTER JOIN Tab_Employee b
Result :
DepID DepName EmpID DepName
1 Accounts 3 Rakesh
2 Sales 4 Omkar
3 HR 1 Siddhesh
4 Technical 2 Sumit
4 Technical 5 Shailesh

Right Outer Join ( Example )
Query :
SELECT a.DepID , a.DepName , b.EmpID , b.EmpName
FROM Tab_Department a
RIGHT OUTER JOIN Tab_Employee b
Result :
DepID DepName EmpID DepName
3 HR 1 Siddhesh
4 Technical 2 Sumit
1 Accounts 3 Rakesh
2 Sales 4 Omkar
4 Technical 5 Shailesh

Full Outer Join ( Example )
Query :
SELECT a.EmpID , a.EmpName , b.DepName
FROM Tab_Employee a
FULL OUTER JOIN Tab_Department b
Result :
EmpID EmpName DepName
1 Siddhesh HR
2 Sumit Technical
3 Rakesh Accounts
4 Omkar Sales
5 Shailesh Technical

Cross Joins
This join returns records/rows that are multiplication of record number from
both the tables means each row on left table will related to each row of right
table.
Syntax:
Cross Join Table 2

Scenario
EmpID EmpName
1 Siddhesh
2 Sumit
DepID DepName
1 Accounts
2 Sales
3 HR
4 Technical

Cross Join ( Example )
Query :
SELECT a.EmpID , a.EmpName , Tab_Department.DepName
FROM Tab_Employee a
CROSS JOIN Tab_Department ;
Result : EmpID EmpName DepName
1 Siddhesh Accounts
2 Sumit Accounts
1 Siddhesh Sales
2 Sumit Sales
1 Siddhesh HR
2 Sumit HR
1 Siddhesh Technical
2 Sumit Technical

Sql joins

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Sql joins