Indexes prevent duplicate entries in the column or combination of columns on which it is created. Since SQL indexes are primarily a performance tool, they are most useful when a database grows in size.

Use the CREATE INDEX command to create indexes:
— syntax index_name on table_name(column1, column2,…, columnN); — make an index on a single column make an index products_category on products(category);… — make an index on multiple columns make an index called products_category_brand on products(category, brand_id);