What methods can be used to improve the efficiency of SQL query execution?

To improve the efficiency of executing SQL queries on a database, the following methods can be used:

1. Indexing — creating indexes on columns frequently used in WHERE, JOIN, or ORDER BY clauses.
2. Query optimization — avoid SELECT *, select only necessary fields.
3. Using prepared statements — enhances performance and security.
4. Caching results — if data does not change often, cache query results.
5. Pagination — when retrieving large volumes of data, use LIMIT and OFFSET.
6. Execution plan analysis — use EXPLAIN to understand how the DBMS executes the query.
7. Minimize the number of queries — combine queries, use JOINs instead of multiple separate queries.

Example of a prepared statement in Java with JDBC:

String sql = "SELECT name FROM users WHERE age > ?";
PreparedStatement stmt = connection.prepareStatement(sql);
stmt.setInt(1, 18);
ResultSet rs = stmt.executeQuery();

These methods help reduce load on the database and speed up application response.