SQL Joins

SQL Join statements are used to combine data or rows from two or more tables based on a common field between them.

Different types of Joins are as follows:

1. INNER JOIN : It compares each row of table A with each row of table B to find all of the rows which satisfy the join condition and returns back the result. Value of the common field will be the same.

Syntax:

SELECT columns
FROM tableA
INNER JOIN tableB
ON tableA.required_column = tableB.required_column ;

2) LEFT JOIN : Left join returns all the records from the left table, even if there are no matched in the right table, it shows null where the records are not matched.

Syntax :

SELECT tableA.column1 , tableB.column2
FROM tableA
LEFT JOIN tableB ON tableA.common_field = tableB.common_field
ORDER BY tableA.required_column ;

3) RIGHT JOIN : Returns all the records from the right table , even if there are no matches in the left table , it shows null where the records are not matched.

Syntax:

SELECT tableA.col1 , tableB.col2
FROM tableA
RIGHT JOIN tableB
ON tableA.required_column = tableB.required_column 
ORDER BY tableA.column ;

4) FULL JOIN : Full Join combines the results of both left and right tables and returns the records.

Syntax :

SELECT tableA.col1 , tableB.col2
FROM tableA
FULL JOIN tableB
ON tableA.required_column = tableB.required_column ;

Hope you find this helpful.

This story will give you an understanding about 4 types of joins.

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