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A database transaction signifies a unit of work performed within a database management system against a database and treated coherently, and reliably independently of other transactions.

Transactions in a database environment have two purposes:

1. To provide reliable units of work that allow correct recovery from failures and keep a database consistent even in cases of system failure, when ex*****on stops and many operations upon a database remain uncompleted, with unclear status.

2. To provide isolation between programs accessing a database concurrently.
If this isolation is not given, the programs' outcomes are possibly erroneous.

A database transaction, by definition, must be atomic (it must either be complete in its entirety or have no effect whatsoever), consistent (it must conform to existing constraints in the database), isolated (it must not affect other transactions), and durable (it must get written to persistent storage).

Database practitioners often refer to these properties of database transactions using the acronym ACID.

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Relational database design (RDD) models’ information and data into a set of tables with rows and columns. Each row of a relation/table represents a record, and each column represents an attribute of data. The Structured Query Language (SQL) is used to manipulate relational databases. The design of a relational database is composed of four stages, where the data are modeled into a set of related tables. The stages are −

* Define relations/attributes
* Define primary keys
* Define relationships
* Normalization

Relational databases differ from other databases in their approach to organizing data and performing transactions. In an RDD, the data are organized into tables and all types of data access are carried out via controlled transactions. Relational database design satisfies the ACID (atomicity, consistency, integrity, and durability) properties required from a database design. Relational database design mandates the use of a database server in applications for dealing with data management problems.




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