Video Summary

SQL indexes are used to speed up data retrieval operations. There are 5 types of indexes in SQL: * **B-tree index:** The most common type of index. It is a balanced tree structure that keeps data sorted and allows for efficient lookups. * **Hash index:** An index that uses a hash function to map data values to a specific location in the index. This type of index is faster than B-tree indexes for lookups on non-clustered tables, but it cannot be used to enforce uniqueness constraints. * **Bitmap index:** An index that stores a bit vector for each row in the table, indicating which columns contain non-null values. This type of index is useful for queries that filter on multiple columns. * **Spatial index:** An index that stores information about the spatial location of data rows. This type of index is useful for queries that perform spatial joins or range queries. * **Full-text index:** An index that stores information about the text content of data rows. This type of index is useful for queries that search for text strings.