What approaches exist for improving the efficiency of executing SQL queries?

The following approaches are used to improve the efficiency of SQL query execution:

• Indexing — creating indexes on columns frequently used in WHERE or JOIN conditions.
• Query optimization — avoiding redundant subqueries, using JOIN instead of nested queries.
• Using EXPLAIN — analyzing the query execution plan to identify bottlenecks.
• Caching results — storing frequently requested data in temporary storage.
• Normalization and denormalization — balancing data structure for read and write optimization.

Example of indexing in PostgreSQL:

CREATE INDEX idx_user_email ON users(email);

This will speed up searching for users by email.