Is `GROUP BY` Always a Suitable Replacement for `DISTINCT` in SQL?

GROUP BY vs. DISTINCT: Two different methods in SQL

The following two SQL queries have the same result:

SELECT column FROM table GROUP BY column;
SELECT DISTINCT column FROM table;

But this raises the question: are the two commands handled differently?

Query processing

Although the output is the same, these commands are processed differently. When using GROUP BY without an aggregate function, SQL Server recognizes that the purpose is to retrieve unique values ​​and optimizes the execution plan as if DISTINCT was used.

Avoid confusion

While the results may be the same, it is important to distinguish between GROUP BY and DISTINCT. GROUP BY is mainly used to group data and perform aggregation operations; while DISTINCT is specifically used to eliminate duplicate values. Misusing these commands can cause unintended consequences.

Analogy

Imagine using a hammer to turn a screw. While it may work in some situations, it's not the best tool. Likewise, using GROUP BY instead of DISTINCT might work, but is less efficient and not suitable for its intended use.

The above is the detailed content of Is `GROUP BY` Always a Suitable Replacement for `DISTINCT` in SQL?. For more information, please follow other related articles on the PHP Chinese website!