Update (database)

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An Update (German: update) is in a database system a writing, data changing access to the database. The update is therefore part of the Data Manipulation Language .

To do this, the physical memory on which the database is located must be changed by a database management system . Since most databases are on hard drives, an update usually triggers write access to a mass storage device .

Since several write and read accesses to the database can always occur simultaneously and, on the other hand, the database should always be in a unique, consistent state (see also ACID ), these accesses must be synchronized. This problem is a special case of the readers-and-writers problem .

Updates can still be part of a transaction .

In SQL , the operations: and are provided for updates . INSERT, UPDATEDELETE

See also

• Selection (computer science)
• CRUD : Create / Read / Updated / Delete; data operations applicable to a particular data set

Individual evidence

1. ↑ Andrew Tanenbaum et al., Operating Systems, 3rd ed., 2006 by Pearson Education, pp. 92 f., ISBN 0-13-142938-8