**Performance Benefits:**

- One query faster than multiple separate queries

- All aggregates computed in single pass

- Reduces network overhead

**Optimization:**

- Use WHERE to filter before GROUP BY

- Index GROUP BY columns

- Consider covering indexes

- Limit grouping dimensions to avoid too many groups

One query with multiple aggregates faster than separate queries

Use WHERE to reduce data before GROUP BY

Index GROUP BY columns

Consider covering indexes

Avoid too many grouping dimensions

Use HAVING only for aggregate conditions

Forgetting non-aggregate columns in GROUP BY

Too many grouping columns creating unreadable results

Using HAVING for row-level conditions

Not considering NULL in grouping columns

Writing separate queries instead of multi-aggregate query