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SQL JOIN

As the name shows, JOIN means to combine something. In case of SQL, JOIN means "to combine two or more tables".

In SQL, JOIN clause is used to combine the records from two or more tables in a database.

Types of SQL JOIN

  1. INNER JOIN
  2. LEFT JOIN
  3. RIGHT JOIN
  4. FULL JOIN

Sample Table

EMPLOYEE

EMP_ID EMP_NAME CITY SALARY AGE
1 Angelina Chicago 200000 30
2 Robert Austin 300000 26
3 Christian Denver 100000 42
4 Kristen Washington 500000 29
5 Russell Los angels 200000 36
6 Marry Canada 600000 48

PROJECT

PROJECT_NO EMP_ID DEPARTMENT
101 1 Testing
102 2 Development
103 3 Designing
104 4 Development

1. INNER JOIN

In SQL, INNER JOIN selects records that have matching values in both tables as long as the condition is satisfied. It returns the combination of all rows from both the tables where the condition satisfies.

Syntax

Query

Output

EMP_NAME DEPARTMENT
Angelina Testing
Robert Development
Christian Designing
Kristen Development

2. LEFT JOIN

The SQL left join returns all the values from left table and the matching values from the right table. If there is no matching join value, it will return NULL.

Syntax

Query

Output

EMP_NAME DEPARTMENT
Angelina Testing
Robert Development
Christian Designing
Kristen Development
Russell NULL
Marry NULL

3. RIGHT JOIN

In SQL, RIGHT JOIN returns all the values from the values from the rows of right table and the matched values from the left table. If there is no matching in both tables, it will return NULL.

Syntax

Query

Output

EMP_NAME DEPARTMENT
Angelina Testing
Robert Development
Christian Designing
Kristen Development

4. FULL JOIN

In SQL, FULL JOIN is the result of a combination of both left and right outer join. Join tables have all the records from both tables. It puts NULL on the place of matches not found.

Syntax

Query

Output

EMP_NAME DEPARTMENT
Angelina Testing
Robert Development
Christian Designing
Kristen Development
Russell NULL
Marry NULL





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