Joins in SQL servers are used to query for retrieve data from 2 or more related tables. A Join clause is used to combine rows from one , two or more tables, based on a related column.
In SQL, a join operation combines rows from two or more tables based on a related column between them. The result of a join is a new table that contains only the rows where the join condition is met. There are several types of joins in SQL, including:
There are three types of JOINS.
1. CROSS JOIN
2. INNER JOIN
3. OUTER JOIN
Outer Joins are 3 types
1. Left Join or Left Outer Join
2. Right Join or Right Outer Join
3. Full Join or Full Outer Join
- INNER JOIN: Returns only the rows where there is a match in both tables.
- LEFT JOIN (or LEFT OUTER JOIN): Returns all rows from the left table and the matching rows from the right table. If there is no match, NULL values will be returned for the right table's columns.
- RIGHT JOIN (or RIGHT OUTER JOIN): Returns all rows from the right table and the matching rows from the left table. If there is no match, NULL values will be returned for the left table's columns.
- FULL OUTER JOIN: Returns all rows from both tables, and for the non-matching rows, NULL values will be returned for the columns of the table that does not have a matching row.
The join condition is specified in the ON clause of the join statement, and it determines which rows from the two tables are combined.