Advance SQL tricks.

Certainly! Here are a few advanced SQL tricks that can help you optimize and enhance your SQL queries:

1. Indexing:
   Indexing is a technique used to improve the performance of database queries by creating indexes on specific columns. Indexes allow the database to quickly locate and retrieve the data, especially when working with large tables. By identifying the columns frequently used in WHERE clauses or JOIN conditions, you can create indexes on those columns to speed up query execution.

2. Window Functions:
   Window functions allow you to perform calculations across a set of rows that are related to the current row. They are particularly useful when you need to calculate running totals, rankings, or moving averages.

3. Common Table Expressions (CTEs):
   CTEs allow you to define temporary result sets that can be referenced multiple times within a single query. They are particularly useful when you need to break down complex queries into smaller, more manageable parts.

4. Conditional Aggregation:
   Conditional aggregation allows you to perform aggregations based on specific conditions. For example, you may want to calculate the average salary for each department, excluding salaries below a certain threshold.

These advanced SQL techniques can significantly enhance your query performance, flexibility, and ability to handle complex data manipulations. However, it's essential to consider the specific database system you are using, as some techniques may vary slightly across different DBMSs.