What types of indexes would you create for a database table to improve query performance?

To improve query performance on a database table, the following types of indexes are usually created:

• Primary Key — a unique index that provides quick access to rows by a unique identifier.
• Unique Indexes — ensure the uniqueness of values in a column and speed up searches.
• Non-unique Indexes — accelerate searches on frequently used columns, such as foreign keys or filter fields.
• Composite Indexes — index multiple columns together, useful for queries filtering by several fields.
• Full-text Indexes — for fast searching of text data.

The choice of indexes depends on the types of queries most frequently executed. For example, if searches are often performed by date and status, a composite index on these columns should be created.

Example of creating an index in SQL:

CREATE INDEX idx_user_email ON users(email);

Or a composite index:

CREATE INDEX idx_orders_date_status ON orders(order_date, status);