What is an outer join in Oracle?
An outer join extends the result of a simple join. An outer join returns all rows that satisfy the join condition and also returns some or all of those rows from one table for which no rows from the other satisfy the join condition.
How does full outer join work in Oracle?
A full outer join performs a join between two tables that returns the results of an INNER join as well as the results of a left and right outer join. This following query retrieves all rows in the employees table, even if there is no match in the departments table.
Does outer join use index?
2 Answers. And you should not need any form of USE INDEX . (And don’t use the funny apostrophes: ‘york’ .) ( OUTER is optional and has no impact.)
What is full outer join?
In theory, a full outer join is the combination of a left join and a right join. The full outer join includes all rows from the joined tables whether or not the other table has the matching row.
What is the function of right outer join?
What is the function of a right outer join? Explanation: The right outer join operation preserves the tuples named after the operation.
What is the difference between join and outer join?
Joins in SQL are used to combine the contents of different tables. The major difference between inner and outer joins is that inner joins result in the intersection of two tables, whereas outer joins result in the union of two tables.
Is a FULL OUTER JOIN possible in Oracle?
Oracle supports inner join, left join, right join, full outer join and cross join. Note that you can join a table to itself to query hierarchical data using an inner join, left join, or right join. This kind of join is known as self-join.
What is the difference between “inner join” and “outer join”?
Key Differences Between Inner Join and Outer Join The basic difference between the Inner Join and Outer Join is that inner join compares and combine only the matching tuples from both the tables. The database size of the resultant obtained from the Inner Join is smaller that Outer Join. There are three types of the Outer Join Left Outer Join, Righ Outer Join, and Full Outer Join.
How do inner joins and outer joins work?
Joins are the most common forms of SQL selects. Inner joins connect two or more tables together by comparing rows and produce a row of output only if the comparison of the rows returns true . Outer joins can produce a row of output even if the comparison does not return true .
Is there inner join and outer join performance difference?
In case there are a large number of rows in the tables and there is an index to use, INNER JOIN is generally faster than OUTER JOIN. Generally, an OUTER JOIN is slower than an INNER JOIN as it needs to return more number of records when compared to INNER JOIN.