Question

List join types in the order of how many records each returns (most to least)

Answer 1

Join types in SQL, ordered from most to least records returned, are: CROSS JOIN, FULL OUTER JOIN, LEFT JOIN, RIGHT JOIN, and INNER JOIN, with CROSS JOIN potentially producing the largest number of records as it returns a Cartesian product.

Step-by-step explanation:

When working with SQL and databases, the number of records returned by different join types can vary depending on the specific data within the tables being joined. However, in general, the join types, ordered from those that potentially return the most records to the least, are as follows:

1. CROSS JOIN: Returns the Cartesian product of both tables, meaning every single combination of rows from both tables. This can result in a very large number of records, especially with large tables.
2. FULL OUTER JOIN: Combines the results of both a LEFT JOIN and a RIGHT JOIN. It returns all rows from both tables and fills in NULLs for missing matches on either side.
3. LEFT JOIN (also known as LEFT OUTER JOIN): Returns all records from the left table and the matched records from the right table. If there is no match, the result is NULL on the right side.
4. RIGHT JOIN (also known as RIGHT OUTER JOIN): Similar to a LEFT JOIN but returns all records from the right table and the matched records from the left table, with NULLs for non-matching rows on the left side.
5. INNER JOIN: Returns records that have matching values in both tables. It typically returns fewer rows than LEFT or RIGHT JOIN because it only includes matching pairs.

It's important to note that the actual number of records returned from a join operation will depend on the data and how the tables' keys correlate with each other.