When should indexing be applied in a database?

Database indexing should be used when:

• There are frequent queries with conditions (WHERE), sorting (ORDER BY), or joins (JOIN) on certain columns.
• The table contains a large number of records, and searching without indexes becomes slow.
• You need to speed up data retrieval, especially when filtering by frequently used fields.

However, indexes occupy additional space and slow down insert, update, and delete operations, so they should be created only when necessary.

Example: if you have a Users table with an Email field, and you often search users by email, it makes sense to create an index on this field:

CREATE INDEX idx_users_email ON Users(Email);

This will speed up queries like SELECT * FROM Users WHERE Email = 'example@example.com'.