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What MySQL returns if I do not use the keyword ‘RIGHT’ or ‘LEFT’ while writing the query for RIGHT JOIN or LEFT JOIN?
In both the cases i.e. on not using ‘RIGHT’ or ‘LEFT’ keyword in the query, MySQL will return the result by taking it as INNER JOIN query. It is because the only difference between RIGHT, LEFT and INNER JOIN is the keyword of RIGHT or LEFT. To understand it, we are taking the example of two tables named tbl_1 and tbl_2 which are having following data −
mysql> Select * from tbl_1; +----+--------+ | Id | Name | +----+--------+ | 1 | Gaurav | | 2 | Rahul | | 3 | Raman | | 4 | Aarav | +----+--------+ 4 rows in set (0.00 sec) mysql> Select * from tbl_2; +----+---------+ | Id | Name | +----+---------+ | A | Aarav | | B | Mohan | | C | Jai | | D | Harshit | +----+---------+ 4 rows in set (0.00 sec)
Now, the query for RIGHT JOIN with keyword RIGHT can be as follows −
mysql> SELECT tbl_1.id,tbl_2.id FROM tbl_1 RIGHT JOIN tbl_2 ON tbl_1.name = tbl_2.name; +------+----+ | id | id | +------+----+ | 4 | A | | NULL | B | | NULL | C | | NULL | D | +------+----+ 4 rows in set (0.00 sec)
Now, in the following query we are not using the keyword RIGHT −
mysql> Select tbl_1.id,tbl_2.id FROM tbl_1 JOIN tbl_2 ON tbl_1.name = tbl_2.name; +----+----+ | id | id | +----+----+ | 4 | A | +----+----+ 1 row in set (0.00 sec)
From the above result set, we can observe the difference that without using keyword ‘RIGHT’, MySQL takes it as a query for INNER JOIN and return the result accordingly.
Now, the query for LEFT JOIN with keyword LEFT can be as follows −
mysql> SELECT tbl_1.id,tbl_2.id FROM tbl_1 LEFT JOIN tbl_2 ON tbl_1.name = tbl_2.name; +----+------+ | id | id | +----+------+ | 1 | NULL | | 2 | NULL | | 3 | NULL | | 4 | A | +----+------+ 4 rows in set (0.02 sec)
Now, in the following query we are not using the keyword LEFT −
mysql> Select tbl_1.id,tbl_2.id FROM tbl_1 JOIN tbl_2 ON tbl_1.name = tbl_2.name; +----+----+ | id | id | +----+----+ | 4 | A | +----+----+ 1 row in set (0.00 sec)
From the above result set, we can observe the difference that without using the keyword ‘LEFT’, MySQL takes it as query for INNER JOIN and return the result accordingly.
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