What is indexing & how does it work?

Indexing is a way of sorting a number of records on multiple fields. Creating an index on a field in a table creates another data structure which holds the field value, and a pointer to the record it relates to. This index structure is then sorted, allowing Binary Searches to be performed on it.

What is an index in SQL?

Every index is associated with a table and has a key, which is formed by one or more table columns. When a query needs to access a table that has an index, the database can decide to use the index to retrieve records faster. If you like learning SQL using hands-on exercises, then you’ve got to try All Forever SQL Package. How Does an Index Work?

What is a non-clustered index?

The non-clustered indexes are really just extra indexes - you have the index keys pointing to page numbers (from the clustered index) where all incidences of that data can be found. An index is used to speed up the performance of queries. It does this by reducing the number of database data pages that have to be visited/scanned.

What are the disadvantages of indexing indices?

The downside to indexing is that these indices require additional space on the disk since the indices are stored together in a table using the MyISAM engine, this file can quickly reach the size limits of the underlying file system if many fields within the same table are indexed. How does it work?