What is an index in the context of database query optimization?
- A column that uniquely identifies each row in a table
- A data structure that improves the speed of data retrieval operations on a database table
- A set of rules defining the relationships among data in a database
- A virtual table derived from the data in the underlying table
An index in the context of database query optimization is a data structure that improves the speed of data retrieval operations on a database table. Indexes are created on one or more columns of a table to facilitate faster data access. When a query is executed that involves the indexed columns, the database engine can use the index to quickly locate the relevant rows, thereby optimizing the query performance.
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