DATA PROCESSING NOTE ON INDEXING
- 1. INDEXING Indexing is a way to optimize the performance of a database by minimizing the number of disk accesses required when a query is processed. It is a data structure technique which is used to quickly locate and access the data in a database.
- 2. ATTTIBUTES OF INDEXES The indexing has various attributes: Access Types: This refers to the type of access such as value based search, range access, etc. Access Time: It refers to the time needed to find particular data element or set of elements. Insertion Time: It refers to the time taken to find the appropriate space and insert a new data. Deletion Time: Time taken to find an item and delete it as well as update the index structure. Space Overhead: It refers to the additional space required by the index.
- 3. TYPES OF INDEXING: a. For every search key value in the data file, there is an index record. b. This record contains the search key and also a reference to the first data record with that search key value.
- 4. Sparse Index: The index record appears only for a few items in the data file. Each item points to a block as shown. To locate a record, we find the index record with the largest search key value less than or equal to the search key value we are looking for
- 5. Clustered Indexing When more than two records are stored in the same file, these types of storing known as cluster indexing. By using the cluster indexing we can reduce the cost of searching reason being multiple records related to the same thing are stored at one place and it also gives the frequent joining of more than two tables (records). Clustered index is like dictionary; in the dictionary, sorting order is alphabetical and there is no separate index page.
- 6. Non-Clustered index is an index structure separate from the data stored in a table that reorders one or more selected columns. The non-clustered index is created to improve the performance of frequently used queries not covered by a clustered index. It’s like a textbook; the index page is created separately at the beginning of that book