Mysql Left Join

Mysql Left Join return you the set of records of right table matches with the left table. The unmatchable records from right table with the left table are specified by null values.

Understand with Example

The Tutorial illustrate an example from Mysql Left Join. To understand this example, we create a table roseindia defined with required fieldname and data type respectively.

Query to Create Table named roseindia:-

mysql> CREATE TABLE roseindia (               
            -> Empid int(11),          
             ->firstname varchar(30),  
            -> city varchar(30)        
          -> );
Query OK, 0 rows affected (0.05 sec)

Query to insert data into Table named roseindia:-

The insert into adds the records or rows into table 'roseindia'.

mysql>  insert into roseindia values(01,'Girish','Nainital');
Query OK, 1 row affected (0.02 sec)

mysql>  insert into roseindia values(02,'Komal','Merrut');
Query OK, 1 row affected (0.00 sec)

mysql>  insert into roseindia values(03,'Amit','Lucknow');
Query OK, 1 row affected (0.02 sec)

mysql>  insert into roseindia values(04,'Sandeep','Lucknow');
Query OK, 1 row affected (0.03 sec)

Query to view data of Table named roseindia:-

mysql> select * from roseindia;

Output:-

+-------+-----------+----------+
| Empid | firstname | city     |
+-------+-----------+----------+
|     1 | Girish    | Nainital |
|     2 | Komal     | Merrut   |
|     3 | Amit      | Lucknow  |
|     4 | Sandeep   | Lucknow  |
+-------+-----------+----------+
4 rows in set (0.00 sec)

Query to Create Table newstrack:-

Now create another table 'newstrack'.The create table statement is used to create table newstrack.

mysql> CREATE TABLE newstrack (               
        ->     Empid int(11),          
         ->    firstname varchar(10),  
         ->    email varchar(30) 
          -> );
Query OK, 0 rows affected (0.03 sec)

Query to insert data into Table named newstrack:-

mysql>  insert into newstrack values(01,'Suman','[email protected]');
Query OK, 1 row affected (0.02 sec)

mysql>  insert into newstrack values(02,'Ravi','[email protected]');
Query OK, 1 row affected (0.01 sec)

mysql>  insert into newstrack values(03,'Santosh','[email protected]');
Query OK, 1 row affected (0.01 sec)

Query to view data of Table named newstrack:-

mysql> select * from newstrack;

Output:-

+-------+-----------+------------------+
| Empid | firstname | email            |
+-------+-----------+------------------+
|     1 | Suman     | girish.gmail.com |
|     2 | Ravi      | komal.gmail.com  |
|     3 | Santosh   | Amit.gmail.com   |
+-------+-----------+------------------+
3 rows in set (0.00 sec)

Left Join:-

Query to join the data of the above two tables named roseindia and newstrack using left outer join:-

The below query return you the set of records from newstrack matches with the left table 'roseindia'. The query also display unmatchable records from table 'newstrack' with table 'roseindia' specified with null.

mysql> SELECT * FROM roseindia AS R
    ->      LEFT JOIN newstrack AS N
    ->      ON R.EmpId = N.EmpId;

Output:-

+-------+-----------+----------+-------+-----------+------------------+
| Empid | firstname | city     | Empid | firstname | email            |
+-------+-----------+----------+-------+-----------+------------------+
|     1 | Girish    | Nainital |     1 | Suman     | girish.gmail.com |
|     2 | Komal     | Merrut   |     2 | Ravi      | komal.gmail.com  |
|     3 | Amit      | Lucknow  |     3 | Santosh   | Amit.gmail.com   |
|     4 | Sandeep   | Lucknow  |  NULL | NULL      | NULL             |
+-------+-----------+----------+-------+-----------+------------------+
4 rows in set (0.00 sec)

Mysql Left Join

Mysql Left Join

Mysql Left Join

Left Join:-

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