Natural Join vs. Inner Join: What's the Key Difference in Column Inclusion and Result Size?

Understanding the Distinct Features of Natural Join and Inner Join

In the realm of database management systems, join operations play a crucial role in combining data from multiple tables based on common attributes to obtain meaningful insights. Natural join and inner join are two closely related join types that exhibit specific differences in their results.

Column Inclusion Difference

A key distinction between natural join and inner join lies in the number of columns returned in the joined result. A natural join automatically eliminates any common column shared between the joined tables, resulting in a result that includes only the unique columns from each table.

For instance, consider two tables, TableA and TableB, with the following columns:

Performing a natural join on these tables using Column1 as the joining attribute will only include Column2 and Column3 in the result, as Column1 is automatically excluded due to its presence in both tables.

Joining Column Specification

Another difference concerns the specification of joining columns. An inner join requires explicit specification of the joining columns, using either the USING clause or the ON clause, while a natural join does not require such specification. The join is performed on the common column(s) shared by both tables.

Result Size

Typically, a natural join results in a smaller number of rows compared to an inner join because it filters out duplicate rows caused by shared columns. This is due to the automatic elimination of redundant columns.

Conclusion

In summary, natural join and inner join differ primarily in the inclusion of common columns in their results. Natural join excludes common columns, producing a more compact result, while inner join includes all columns, potentially leading to duplication.

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