PRIMARY INDEX IN DBMS | INDEXING IN DATABASE | INDEXING IN DBMS | PRIMARY INDEX скачать в хорошем качестве

PRIMARY INDEX IN DBMS | INDEXING IN DATABASE | INDEXING IN DBMS | PRIMARY INDEX

What is Indexing in Database? A database index is a DATA STRUCTURE that improves the SPEED OF DATA RETRIEVAL operations on a database table. It is used to LOCATE AND ACCESS the data in a database table QUICKLY, this process is called as INDEXING. Indexing is used to OPTIMIZE the performance of a database by MINIMIZING THE NUMBER OF DISK ACCESSES REQUIRED when a QUERY IS PROCESSED. Indexes are created using a FEW DATABASE COLUMNS. An INDEX is a small table having ONLY TWO COLUMNS. The FIRST COLUMN comprises a copy of the PRIMARY OR CANDIDATE KEY of a table. Its SECOND COLUMN contains a SET OF POINTERS for holding the ADDRESS of the DISK BLOCK where that SPECIFIC KEY value stored. PRIMARY INDEX: Defined on an ordered data file, which is based on a PRIMARY KEY field of the relation. DENSE INDEX: Stores ALL SEARCH-KEY values, needs MORE SPACE, makes SEARCHING FASTER. SPARSE INDEX:Stores only some SEARCH-KEY values, needs LESS SPACE, LESS MAINTENANCE overhead