Difference between revisions of "SQL Indexing"
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* An index is a distinct structure in the DB that requires its own space. | * An index is a distinct structure in the DB that requires its own space. | ||
* A DB index is similar to index of a book - key concept is all entries are arranged in a well-defined order. Finding data in an ordered set is fast and easy because the sort order determines each entries position. | * A DB index is similar to index of a book - key concept is all entries are arranged in a well-defined order. Finding data in an ordered set is fast and easy because the sort order determines each entries position. | ||
| + | * A DB index however undergoes constant change. Whenever INSERT, UPDATE, DELETE's are executed, the index must also be updated without moving around large amounts of data. | ||
| + | * The DB combines two data structures for providing indexing - doubly linked lists and search trees. | ||
Revision as of 04:08, 2 October 2014
These are notes that I took about SQL Indexing from http://use-the-index-luke.com
Introduction
- An index makes a SQL query fast.
- An index is a distinct structure in the DB that requires its own space.
- A DB index is similar to index of a book - key concept is all entries are arranged in a well-defined order. Finding data in an ordered set is fast and easy because the sort order determines each entries position.
- A DB index however undergoes constant change. Whenever INSERT, UPDATE, DELETE's are executed, the index must also be updated without moving around large amounts of data.
- The DB combines two data structures for providing indexing - doubly linked lists and search trees.
