JOINS in SQL

INNER JOIN

• A JOIN clause is used to combine rows from two or more tables, based on a related column between them.

INNER JOIN Syntax

Called INNER JOIN or just JOIN

The INNER JOIN keyword selects records that have matching values in both tables.

Syntax of a INNER JOIN:

SELECT Column_Name(s)
FROM Table_1
INNER JOIN Table_2 -- or just JOIN
ON Table_1.Column_Name = Table_2.Column_Name  -- What they have in common

Example of an INNER JOIN:

SELECT employee.emp_id, employee.first_name, branch.branch_name
FROM employee
INNER JOIN branch    -- or just use the keyword JOIN
ON employee.emp_id = branch.mgr_id

LEFT JOIN

The LEFT JOIN will grab everything from the left table and any missing values will be NULL

Example of an LEFT JOIN:

SELECT employee.emp_id, employee.first_name, branch.branch_name
FROM employee
LEFT JOIN branch    
ON employee.emp_id = branch.mgr_id

RIGHT JOIN

The RIGHT JOIN will grab everything from the right table and any missing values will be NULL

Example of an RIGHT JOIN:

SELECT employee.emp_id, employee.first_name, branch.branch_name
FROM employee
RIGHT JOIN branch    
ON employee.emp_id = branch.mgr_id

FULL JOIN

• FULL or (OUTER) JOIN returns unmatched rows from both tables.

NOTE: A Full join isnt supported in MySQL or SQLite which I’ve used the most