1. Indexing :
Indexing, as name suggests, is a technique or mechanism generally used to speed up access of data. Index is basically a type of data structure that is used to locate and access data in database table quickly. Indexes can easily be developed or created using one or more columns of database table.
2. Hashing :
Hashing, as name suggests, is a technique or mechanism that uses hash functions with search keys as parameters to generate address of data record. It calculates direct location of data record on disk without using index structure. A good hash functions only uses one-way hashing algorithm and hash cannot be converted back into original key. In simple words, it is a process of converting given key into another value known as hash value or simply hash.
Difference between Indexing and Hashing in DBMS : Indexing Hashing
It is a technique that allows to quickly retrieve records from database file. It is a technique that allows to search location of desired data on disk without using index structure. It is generally used to optimize or increase performance of database simply by minimizing number of disk accesses that are required when a query is processed. It is generally used to index and retrieve items in database as it is faster to search that specific item using shorter hashed key rather than using its original value. It offers faster search and retrieval of data to users, helps to reduce table space, makes it possible to quickly retrieve or fetch data, can be used for sorting, etc. It is faster than searching arrays and lists, provides more flexible and reliable method of data retrieval rather than any other data structure, can be used for comparing two files for quality, etc. Its main purpose is to provide basis for both rapid random lookups and efficient access of ordered records. Its main purpose is to use math problem to organize data into easily searchable buckets. It is not considered best for large databases and its good for small databases. It is considered best for large databases. Types of indexing includes ordered indexing, primary indexing, secondary indexing, clustered indexing. Types of hashing includes static and dynamic hashing. It uses data reference to hold address of disk block. It uses mathematical functions known as hash function to calculate direct location of records on disk. It is important because it protects file and documents of large size business organizations, and optimize performance of database. It is important because it ensures data integrity of files and messages, takes variable length string or messages and compresses and converts it into fixed length value.
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