What is the method for performing multi-table join queries in SQL?

1 year ago
Benjamin Taylor
2 minutes

In SQL, you can use the JOIN clause to perform multi-table join queries. The JOIN clause is used to connect records from multiple tables, allowing data from different tables to be displayed in the query results. Common JOIN types include:

  1. INNER JOIN: Returns records that have matching values in both tables, only including data that has a match in the result set.
SELECT *
FROM table1
INNER JOIN table2 ON table1.column = table2.column;
  1. LEFT JOIN (or LEFT OUTER JOIN): Returns all records from the left table, as well as any matching records from the right table based on the join condition (if there are any matches).
SELECT *
FROM table1
LEFT JOIN table2 ON table1.column = table2.column;
  1. RIGHT JOIN (or RIGHT OUTER JOIN): Returns all records from the right table, as well as any matching records from the left table (if there are any matches).
SELECT *
FROM table1
RIGHT JOIN table2 ON table1.column = table2.column;
  1. FULL JOIN (or FULL OUTER JOIN): Returns all records from both the left and right tables, connecting them if there is a match and displaying NULL if there is no match.
SELECT *
FROM table1
FULL JOIN table2 ON table1.column = table2.column;

Apart from the basic JOIN types mentioned above, there are also other advanced connection methods that can be used, such as CROSS JOIN (Cartesian product), SELF JOIN, etc., to meet different querying needs.

bannerAds