The SQL Join clause is used to combine records (rows) from two or more tables in a SQL database based on a related column between the two.
There are four different types of JOINs in SQL:
- (INNER) JOIN: Retrieves records that have matching values in both tables involved in the join. This is the widely used join for queries.
SELECT *
FROM Table_A
JOIN Table_B;
SELECT *
FROM Table_A
INNER JOIN Table_B;
- LEFT (OUTER) JOIN: Retrieves all the records/rows from the left and the matched records/rows from the right table.
SELECT *
FROM Table_A A
LEFT JOIN Table_B B
ON A.col = B.col;
- RIGHT (OUTER) JOIN: Retrieves all the records/rows from the right and the matched records/rows from the left table.
SELECT *
FROM Table_A A
RIGHT JOIN Table_B B
ON A.col = B.col;
- FULL (OUTER) JOIN: Retrieves all the records where there is a match in either the left or right table.
SELECT *
FROM Table_A A
FULL JOIN Table_B B
ON A.col = B.col;
