sql right join

sql right join

Posted by Ervin Adams on December 18, 2022

sql right join

sql right join

Posted by Ervin Adams on December 18, 2022

The RIGHT JOIN is a clause that allows you to query two or more tables in sql used to collect data.

Although even if there are no matches in the left table, all the relevant rows will be returned in the right table.

Therefore, the RIGHT JOIN returns all the values from the table and matching values from the left table or NULL if there is no match

Here is an example of a RIGHT JOIN in sql below:

SELECT tableA.columnA, tableB.columnB
FROM tableA
RIGHT JOIN tableB
ON tableA.column = tableB.column;

Here is an example:

Table A are students in a school

+----+----------+-----+------------+
| id | name     | age | student_num|
+----+----------+-----+------------+
|  1 | Kevin    |  15 | 078657     |
|  2 | Dane     |  16 | 076565     |
|  3 | James    |  15 | 087675     |
|  4 | Sandy    |  14 | 075657     |
|  5 | Ava      |  16 | 085654     |
|  6 | Zuri     |  15 | 075555     |
+----+----------+-----+------------+

Table B are adminstrations details

+----+-----------+--------+---------------------+------------+
| id | subject   | teacher| date                | student_id |
+----+-------------+----------------------------+------------+
|  1 | Math      | Mr Jack| 2022-10-08 00:00:00 | 1          |
|  2 | English   | Mrs Jen| 2022-10-08 00:00:00 | 1          |
|  3 | Physics   | Mrs Lin| 2021-09-08 00:00:00 | 4          |
|  4 | Geography | Mr Dan | 2020-09-08 00:00:00 | 3          |
+----+-------------+---------+------------------+------------+

Let us do the RIGHT JOIN on the tables above:

SELECT  id, name, student_num, subject, date
   FROM students
   RIGHT JOIN administrations
   ON students.id = administrations.student_id;

Result

+----+----------+-------------+--------------------------------+
| id | name     | student_num | subject  | date                |
+----+----------+-------------+--------------------------------+
|  1 | Kevin    | 078657      | Math     | 2022-10-08 00:00:00 |               
|  1 | Kevin    | 078657      | English  | 2022-10-08 00:00:00 |
|  4 | Sandy    | 075657      | Physics  | 2021-09-08 00:00:00 |
|  3 | James    | 087675      | Geography| 2020-09-08 00:00:00 |
+----+----------+-------------+--------------------------------+

 

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