**SQL query performance optimization techniques**

 1. **Use Indexing**:

   - Add indexes on frequently filtered or joined columns.

2. **Avoid SELECT ***:

   - Retrieve only required columns.

3. **Use Joins Efficiently**:

   - Prefer inner joins over outer joins when possible.

   - Join on indexed columns.

4. **Optimize WHERE Clauses**:

   - Avoid functions on columns in `WHERE` (e.g., `WHERE YEAR(date) = 2023` → `WHERE date >= '2023-01-01'`).

5. **Use EXISTS Instead of IN**:

   - `EXISTS` is often faster for subqueries.

6. **Limit the Rows**:

   - Use `LIMIT` or `TOP` to fetch only needed rows.

7. **Partition Large Tables**:

   - Use table partitioning for large datasets.

8. **Avoid Correlated Subqueries**:

   - Replace them with joins or CTEs.

9. **Use Query Execution Plans**:

   - Analyze and tune queries based on execution plans.

10. **Batch Updates and Inserts**:

    - Split large operations into smaller batches.

These techniques improve query performance in real-world scenarios.