Differences between Left and Right Join

The main difference between these joins is the inclusion of non-matched rows. The LEFT JOIN includes all records from the left side and matched rows from the right table, whereas RIGHT JOIN returns all rows from the right side and unmatched rows from the left table.

1. What is difference between left join and left outer join?
2. What is the difference between right join and right outer join?
3. Why use right join instead of left join?
4. IS LEFT JOIN faster than right join?
5. What is the function of a left outer join?
6. WHY IS LEFT JOIN slow?
7. What is a natural join?
8. How does right outer join work?
9. What does LEFT JOIN mean?
10. IS LEFT JOIN inner or outer?
11. Why we use left join in SQL?
12. How does LEFT JOIN work?

What is difference between left join and left outer join?

Left Outer Join returns all the rows from the table on the left and columns of the table on the right is null padded. Left Outer Join retrieves all the rows from both the tables that satisfy the join condition along with the unmatched rows of the left table.

What is the difference between right join and right outer join?

4 Answers. There is no difference between RIGHT JOIN and RIGHT OUTER JOIN . Both are the same. That means that LEFT JOIN and LEFT OUTER JOIN are the same.

Why use right join instead of left join?

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.

IS LEFT JOIN faster than right 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.

What is the function of a left outer join?

A LEFT OUTER JOIN is one of the JOIN operations that allow you to specify a join clause. It preserves the unmatched rows from the first (left) table, joining them with a NULL row in the shape of the second (right) table.

WHY IS LEFT JOIN slow?

The LEFT JOIN query is slower than the INNER JOIN query because it's doing more work. From the EXPLAIN output, it looks like MySQL is doing nested loop join. ... For the INNER JOIN query, MySQL is using an efficient "ref" (index lookup) operation to locate the matching rows.

What is a natural join?

A NATURAL JOIN is a JOIN operation that creates an implicit join clause for you based on the common columns in the two tables being joined. Common columns are columns that have the same name in both tables. A NATURAL JOIN can be an INNER join, a LEFT OUTER join, or a RIGHT OUTER join.

How does right outer join work?

RIGHT JOIN: RIGHT JOIN is similar to LEFT JOIN. This join returns all the rows of the table on the right side of the join and matching rows for the table on the left side of join. The rows for which there is no matching row on left side, the result-set will contain null. RIGHT JOIN is also known as RIGHT OUTER JOIN.

What does LEFT JOIN mean?

The LEFT JOIN command returns all rows from the left table, and the matching rows from the right table. The result is NULL from the right side, if there is no match.

IS LEFT JOIN inner or outer?

LEFT JOIN is same as LEFT OUTER JOIN - (Select records from the first (left-most) table with matching right table records.) RIGHT JOIN is same as RIGHT OUTER JOIN - (Select records from the second (right-most) table with matching left table records.) Inner join: Only show rows, when has it data from both of the tables.

Why we use left join in SQL?

The LEFT JOIN clause allows you to query data from multiple tables. It returns all rows from the left table and the matching rows from the right table. ... In short, the LEFT JOIN clause returns all rows from the left table (T1) and matching rows or NULL values from the right table (T2).

How does LEFT JOIN work?

The LEFT JOIN keyword returns all records from the left table (table1), and the matching records from the right table (table2). The result is 0 records from the right side, if there is no match.