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. |02.03 - SQL, DDL and DML .
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The Database Management System (DBMS) is using the
data model when it works with data. There are two
main groups of languages for data manipulation. The
first are procedural languages. When the programmer
is using procedural programming language for data
manipulation the description of data has to be
defined. Then for further work the algorithms on how
to use these data has to be specified.
On the other hand when the non-procedural language
is used there is no need to specify the description
of the data. Query languages are in the group of the
non-procedural languages. When using Query language
the description of the data structure is already in
the database data dictionary. The basic of the query
language command is one sentence or query. The main
purpose to enter queries to the database system is
the manipulation of the database inner structure.
The Query language has two main distinction for
the queries by it's usage. The first subset of
queries is for the data definition (Data Definition
Language Statements or DDL). The second subset
of queries is used for data manipulation (Data
Manipulation Language Statements or DML). During the
time there were many proposals for query languages.
But the main industry standard is the Structured
Query Language (SQL). It is implemented in the most
of the database products.
