How can you optimize query statements in SQLite?

To optimize SQLite queries, you can use the following methods:

1. Create appropriate indexes: Creating indexes on columns frequently used in queries can speed up query execution. You can use the CREATE INDEX statement to create indexes.
2. Analyze query plans using the EXPLAIN statement: The EXPLAIN statement allows you to review the query execution plan generated by the SQLite optimizer, helping to identify potential performance bottlenecks.
3. Avoid using SELECT: try to only query the necessary columns instead of selecting all columns.
4. Avoid using functions in the WHERE clause: utilizing functions in the WHERE clause will prevent indexes from being used, it is recommended to pre-calculate function results or redesign the query.
5. Limit the size of the result set by using LIMIT: If only a portion of the results is needed, you can use LIMIT to restrict the number of queried results.
6. Instead of using UNION, use UNION ALL if you can ensure that the results of the two queries do not contain duplicate records, as UNION ALL does not remove duplicate records.
7. Using EXISTS instead of IN in a query is typically more efficient.

By utilizing the methods above, SQLite query statements can be optimized to enhance query performance.