JOIN vs. INNER JOIN: What's the Real Difference?

Understanding JOIN and INNER JOIN in SQL

Database queries often require combining data from multiple tables. JOIN and INNER JOIN are common methods for achieving this, linking rows based on matching conditions. While functionally equivalent in most scenarios, there are subtle differences worth noting.

Both JOIN and INNER JOIN return only rows where the join condition is met. For example:

SELECT * FROM table1 JOIN table2 ON table1.ID = table2.FK;

is identical to:

SELECT * FROM table1 INNER JOIN table2 ON table1.ID = table2.FK;

Both queries retrieve rows from table1 and table2 only when table1.ID equals table2.FK.

Performance-wise, there's no practical difference. Database optimizers usually choose the most efficient join strategy regardless of whether JOIN or INNER JOIN is used.

However, INNER JOIN enhances readability. The explicit "INNER" keyword clearly distinguishes it from other join types like LEFT JOIN or RIGHT JOIN, improving code clarity, especially in complex queries with multiple joins.

Minor syntax variations might exist across different database systems, but the core functionality remains consistent. Both JOIN and INNER JOIN offer efficient ways to link and retrieve relevant data from multiple tables. Using INNER JOIN is generally preferred for its improved readability.

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