A relational database, based on the relational model, allows the definition of data structures, storage and retrieval operations, and integrity constraints. In such a database the data and relations between them are organized in tables. A table is a collection of records and each record in a table contains the same fields. Certain fields may be designated as keys, which means that searches for specific values of that field will use indexing to speed them up.
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Where fields in two different tables take values from the same set, a join operation can be performed to select records in the two tables by matching values in those fields. Two unique features offered by relational systems are
- Data independence
- A condition that exists when data access is unaffected by changes in the physical data storage characteristics
- SQL (Structured Query Language)
- SQL is a relational database standard data-access language. Nonprocedural processing means that the tables of a relational database can be manipulated in their entirety by special operators; there is no need to iterate tuple by tuple through the relation.
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