ALL CLASS COMPUTER SCIENCE AND DATA PROCESSING NOTES

  INFORMATION PROCESSING AND TRANSMISSION 1

An index is a data structure, a special data structure designed to improve the speed of data retrieval. An index on a file speeds up selections on the search key fields for the index.   CLUSTERED INDEX Clustered index is a type of index which sorts the data rows in the table on their key values. Clustered index exists as sorted row on disk. Clustered index re-orders the table record. Clustered index contains record in the leaf level of the B-tree. NON-CLUSTERED INDEX A Non-clustered index stores the data at one location and indices at another location. The index contains pointers to the location of that data. Non-clustered index is like the index in the back of a chemistry text book. The chemistry text book has some natural order to it: Chapter 1: Matter Chapter 2: Elements Chapter 3: Compounds DENSE INDEX In a dense index, a record is created for every search key valued in the database. This helps you to search faster but needs more space to store index records. In t