What approaches can be used to reduce the execution time of complex queries?

To reduce the execution time of complex queries, the following approaches can be applied:

• Indexing: Creating indexes on columns frequently used in filtering conditions or joins significantly speeds up searches.
• Query optimization: Rewrite queries to reduce the number of joins, use subqueries or aggregations more efficiently.
• Caching: Cache the results of frequently executed queries or intermediate data.
• Parallelization: Break down the query into parts and execute them in parallel if the DBMS supports it.
• Using materialized views: Precomputed query results that are updated on a schedule.
• Execution plan analysis: Use EXPLAIN to understand which operations take the most time and optimize them.

Example of indexing in SQL:

CREATE INDEX idx_user_email ON users(email);

This will speed up searching for users by email.