Left Join
LEFT OUTER JOIN or LEFT JOIN makes the table on the left of the join more dominant. The result will include all the rows from the left table and matched rows from the right table.
SYNTAX:
SELECT T1.Column1, T2.Column2 …
FROM TABLE1 AS T1
LEFT JOIN TABLE2 AS T2
ON T1.COL1 = T2.COL1
Left Join
Table: Employee
EmployeeID FirstName LastName Title HireDate ManagerID
1 George Cruz CEO 12/8/2008 NULL
2 John Mathew Vice President 4/1/2009 1
3 Ethan William Director I 8/8/2009 2
4 Jacob Logan Director II 12/8/2011 3
5 Nathan Mateo Senior Manager 9/3/2009 4
6 Alice Charles Manager I 12/8/2012 5
7 John Robert Manager II 10/8/2011 6
8 Sophia James Manager III 5/8/2011 7
9 Kevin Chan Product Manager 7/8/2011 5
10 Susan Mortiz Solutions Arthitect 1/3/2012 6
11 Martha Miller Systems Arthitect 12/15/2012 10
Table: Location
LocationID LocationCode LocationName
1 L001 San Francisco
2 L002 New York
3 L003 Chicago
4 L004 Los Angeles
Example
Query :
SELECT E.EmployeeID, E.LastName, E.FirstName, L.*
FROM Employee AS E
LEFT JOIN Location AS L ON E.EmployeeLocationID = L.LocationID
Output :
EmployeeID FirstName LastName LocationID LocationCode LocationName
1 George Cruz 1 L001 San Francisco
2 John Mathew 1 L001 San Francisco
3 Ethan William 2 L002 New York
4 Jacob Logan NULL NULL NULL
5 Nathan Mateo 2 L002 New York
6 Alice Charles 1 L001 San Francisco
7 John Robert 2 L002 New York
8 Sophia James NULL NULL NULL
9 Kevin Chan 1 L001 San Francisco
10 Susan Mortiz 1 L001 San Francisco
11 Martha Miller 1 L001 San Francisco
Description :
The above query with LEFT JOIN has Employee table as the dominant table. The query returns all records from the Employee table and only matching records from the Location table. If a row in Employee table does not have matching record in Location table, then the row output will contain NULL value for each column from Location table.

As you can see, since there are no matching row in Location table for EmployeeID 4 and 8, NULL value is returned for each column from Location table. Also notice that the output does not contain all the Locations from Location table. LocationID 3 and 4 are not part of the output because it does not have a matching LocationID in Employee table.