What is an SQL Join and what types do you know?

Operation of concatenating strings from one or more tables based on a related column between them.

Types of SQL JOINs:

• INNER JOIN: Returns rows that have matching values in both tables.
• LEFT JOIN (or LEFT OUTER JOIN): Returns all rows from the left table and the matched rows from the right table. If there is no match, the result is NULL on the right side.
• RIGHT JOIN (or RIGHT OUTER JOIN): Returns all rows from the right table and the matched rows from the left table. If there is no match, the result is NULL on the left side.
• FULL JOIN (or FULL OUTER JOIN): Returns all rows when there is a match in one of the tables. Combines the results of LEFT JOIN and RIGHT JOIN. If there is no match, the result is NULL in the respective side.
• CROSS JOIN: Returns the Cartesian product of rows from both tables (each row of the first table is combined with every row of the second table).

-- Example of INNER JOIN
SELECT *
FROM table1
INNER JOIN table2 ON table1.id = table2.table1_id;

-- Example of LEFT JOIN
SELECT *
FROM table1
LEFT JOIN table2 ON table1.id = table2.table1_id;

-- Example of RIGHT JOIN
SELECT *
FROM table1
RIGHT JOIN table2 ON table1.id = table2.table1_id;

-- Example of FULL JOIN
SELECT *
FROM table1
FULL OUTER JOIN table2 ON table1.id = table2.table1_id;

-- Example of CROSS JOIN
SELECT *
FROM table1
CROSS JOIN table2;