IBM DB2 - SQL Reference Vol 1 v8.2

Peter Kitson

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Sample Chapter From IBM DB2 - SQL Reference Vol 1 v8.2
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Relational databases

A relational database is a database that is treated as a set of tables and manipulated
in accordance with the relational model of data. It contains a set of objects used to
store, manage, and access data. Examples of such objects are tables, views, indexes,
functions, triggers, and packages.

A partitioned relational database is a relational database whose data is managed
across multiple partitions (also called nodes). This separation of data across
partitions is transparent to users of most SQL statements. However, some data
definition language (DDL) statements take partition information into consideration
(for example, CREATE DATABASE PARTITION GROUP). (Data definition
language is the subset of SQL statements used to describe data relationships in a
database.)

A federated database is a relational database whose data is stored in multiple data
sources (such as separate relational databases). The data appears as if it were all in
a single large database and can be accessed through traditional SQL queries.
Changes to the data can be explicitly directed to the appropriate data source.

Structured Query Language (SQL)

SQL is a standardized language for defining and manipulating data in a relational
database. In accordance with the relational model of data, the database is treated
as a set of tables, relationships are represented by values in tables, and data is
retrieved by specifying a result table that can be derived from one or more base
tables.

SQL statements are executed by a database manager. One of the functions of the
database manager is to transform the specification of a result table into a sequence
of internal operations that optimize data retrieval. The transformation occurs in
two phases: preparation and binding.

All executable SQL statements must be prepared before they can be executed. The
result of preparation is the executable or operational form of the statement. The
method of preparing an SQL statement and the persistence of its operational form
distinguish static SQL from dynamic SQL.