Usage of (+) in sql

In SQL, the ( ) operator is used to merge query result sets, filling NULL values in unmatched rows. It allows performing outer joins, avoiding Cartesian products, and comes in two types: left outer join and right outer join. Left and right outer joins will return all rows from the left or right table, filling in NULL values for unmatched rows.

Usage of ( ) in SQL

In SQL query, ( ) operator is used to combine two The query result sets are merged and missing rows are filled with NULL values.

Syntax:

SELECT column_list FROM table1 LEFT|RIGHT (+) JOIN table2 ON join_condition;

Function:

• Outer connection:( ) operation operator allows you to perform an outer join, which returns a result set that contains matching rows from both tables and all rows from one or both tables.
• Fill missing rows:For unmatched rows, the () operator inserts NULL values in the missing table.
• Avoid Cartesian product:In an inner join, if there are no matching rows, the query will return an empty result set. Using the ( ) operator you can fill in missing rows and avoid the Cartesian product.

Type:

• Left Outer Join:LEFT ( ) JOIN returns all rows from the left table and No matching left table rows in the right table are populated with NULL values.
• Right Outer Join:RIGHT ( ) JOIN returns all rows from the right table and fills NULL values for right table rows that do not have a match in the left table.

Example:

Suppose we have the following two tables:

SELECT * FROM students LEFT (+) JOIN courses ON students.id = courses.id;

Result:

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