SQL -Structured Query Language - SQL Joins - Left Join Tutorial

Left Join or Left Outer Join is used to retrieve all the records from the left table ( table which is mentioned first – table1) and the records that are matched from the right table( table which is mentioned second – table2).

We can perform left joins in multiple tables.

The syntax for left joins is-

SELECT column_name1,column_name2,..,column_nameN 
FROM 
table_1 LEFT JOIN table_2 
ON 
table_1.column_name = table_2.column_name;

For example-

SELECT *
FROM 
employees
LEFT JOIN 
job_history
WHERE 
employees.employee_id = job_history.employee_id;

Better to use AS (Alias) for the long table name-

SELECT e.first_name,e.email,e.salary,jh.start_date,jh.end_date 
FROM 
employees as e
left join 
job_history as jh
WHERE 
e.employee_id = jh.employee_id;

Here we will get all records from the left table (employees) and only those records where id will get matched in both employees and job_history table.

Another record that is not matched in the right table (table2) will not get retrieved.