Information Systems
Retrieval of data in SQL can be sped up by the creation of indexes in a table. Explain what an index is and how it works in speeding up data retrieval. Describe one issue that can occur by using too many indexes in a table.
Sample Answer
What is an Index in SQL?
An index in SQL is a data structure that helps in faster retrieval of specific records from a table. It acts as a pointer to the actual data stored in the table, allowing the database engine to quickly locate the desired records without having to scan the entire table.
How Indexes Work
Indexes are typically based on B-trees, which are tree-like data structures that efficiently organize data for fast searching. When an index is created on a particular column in a table, the database engine sorts the values of that column and builds a corresponding B-tree structure.
To retrieve data using an index, the database engine first searches the B-tree structure to identify the exact location of the desired records. This process is much faster than scanning the entire table because the B-tree structure eliminates the need to examine every row.