- Join is use to get information to multiple table base on condition.
- According to our requirement just splitting of information into multiple table using joins we can combine those table to get data
Joins are divided in 3 type:
- Inner Join.
- Outer Join.
- Cross or partition Join.
- If we are getting records from multiple table based on equi condition comes under equi join.
- In the equi-join the comparison we are making between two columns is that they match the same value.
- We can use this method to select certain fields from both tables and only the correct rows will be joined together.
- Using this we can get records from multiple table without equal condition.
Outer Join :
- By using outer join we can get matching and un-matching records from two table.
- Outer joins are divided into 3 type:
- Left Outer Join.
- Right outer Join.
- Full Outer Join.
1.Left Outer Join:
- we can get matching and un-matching record from left side table only matching record from RHS table.
2.Right Outer Join:
- we can get matching and un-matching record from right side table only matching record from LHS table.
3.Full Outer Join:
- It is combination of left and right outer joins use to get the matching and un-matching records from both the tables.
- Using UNION key word we can join this two table.