Final answer:
By default, SQLite creates an index only for the primary key column to ensure uniqueness and efficient data retrieval. No additional indexes are made automatically for other columns or foreign keys, and these must be created manually based on query performance needs.
Step-by-step explanation:
The question pertains to the default indexing behavior of SQLite, a popular relational database management system. SQLite automatically creates a unique index for each primary key column in a table. This index is used to ensure the uniqueness and quick lookup of entries based on the primary key. Besides this, SQLite does not create indexes by default for other columns; instead, it is the responsibility of the database designer or developer to create additional indexes as needed for performance optimization.
When a foreign key relationship is defined, SQLite allows the creation of indexes to improve the performance of queries involving joins, though it does not automatically create indexes for foreign keys. It is a best practice to create indexes on columns that are frequently used in WHERE clauses, join conditions, or order by statements to significantly improve query speeds.