What is a right outer join in SQL?
A right outer join is a method of combining tables. The result includes unmatched rows from only the table that is specified after the RIGHT OUTER JOIN clause. If you are joining two tables and want the result set to include unmatched rows from only one table, use a LEFT OUTER JOIN clause or a RIGHT OUTER JOIN clause.
What is right join in MySQL?
The Right Join is used to joins two or more tables and returns all rows from the right-hand table, and only those results from the other table that fulfilled the join condition. If it finds unmatched records from the left side table, it returns Null value. It is also known as Right Outer Join. …
Why right outer join is needed?
The only reason I can think of to use RIGHT OUTER JOIN is to try to make your SQL more self-documenting. You might possibly want to use left joins for queries that have null rows in the dependent (many) side of one-to-many relationships and right joins on those queries that generate null rows in the independent side.
Can join just be used for 2 tables?
Joins are used to combine the rows from multiple tables using mutual columns. … In that case, you must find a way to SQL Join multiple tables to generate one result set that contains information from these tables. Noting that joins can be applied over more than two tables.
What is self join?
A self JOIN is a regular join, but the table is joined with itself – this is extremely useful for comparisons within a table. Joining a table with itself means that each row of the table is combined with itself and with every other row of the table.
How does Right join work in SQL?
The SQL RIGHT JOIN returns all rows from the right table, even if there are no matches in the left table. This means that if the ON clause matches 0 (zero) records in the left table; the join will still return a row in the result, but with NULL in each column from the left table.
What is outer join with example?
The FULL OUTER JOIN (aka OUTER JOIN ) is used to return all of the records that have values in either the left or right table. For example, a full outer join of a table of customers and a table of orders might return all customers, including those without any orders, as well as all of the orders.
When would you use the SQL Right join command?
When to Use RIGHT JOIN
The RIGHT OUTER JOIN is used when you want to join records from tables, and you want to return all the rows from one table and show the other tables columns if there is a match else return NULL values.
Which join is best in SQL?
SQL join best practices
- Inner joins output the matching rows from the join condition in both of the tables.
- Cross join returns the Cartesian product of both tables.
- Outer join returns the matched and unmatched rows depending upon the left, right and full keywords.
- SQL self-join joins a table to itself.
What is a left and right join?
LEFT JOIN: returns all rows from the left table, even if there are no matches in the right table. RIGHT JOIN: returns all rows from the right table, even if there are no matches in the left table.
IS LEFT join faster than inner join?
A LEFT JOIN is absolutely not faster than an INNER JOIN . In fact, it’s slower; by definition, an outer join ( LEFT JOIN or RIGHT JOIN ) has to do all the work of an INNER JOIN plus the extra work of null-extending the results.