Database application

[I've mainly focused on commercial applications of large databases. Please feel free to add other types of applications]

Databases are in widespread use, especially in the corporate world. Two typical uses are for Online Transaction Processing (OLTP), which usually keeps up with operational data, like payroll, inventory, or in the banking industry, account balances; and Data Warehousing, which brings together large amounts of data for querying or reporting purposes.

OLTP usually involves changing small quantities of data at a time, such as adding a particular person's latest transactions and updating their account summary for a bank account. Reliability and integrity of the data is often critical for this type of application, so ACID database transactions are very important.

The techniques that work well for OLTP usually work poorly or not at all for data warehousing and vice versa. Indexes for speedy access to individual rows are critical for OLTP. Data warehousing usually works with large subsets of the data in a table, where indexes become much less useful. Record updates and deletes perform very slowly when they affect large subsets of data, so those operations are often done by rebuilding the tables instead.

See also : Database