SQL Components
The Structured Query Language is broken up into three com-
ponents: DDL, DML, and DCL.
The Data Definition Language (DDL) component is used to
create tables and establish relationships among tables.
The Data Manipulation Language (DML) component is used
to manage the database by performing such operations as
retrieving data, updating data, deleting data, and navigating
through data.
The Data Control Language (DCL) component is used to
provide security features for the database.
SQL Syntax
In order to implement SQL, you must follow a series of rules
that state how SQL script must be scripted. These rules are
referred to as syntax. When a syntax rule is violated, the DBMS
will return a system-generated error message to the screen.
Stick to the syntax and you can reduce the probability of seeing
these unpleasant messages.
The SQL language is made up of a series of keywords, state-
ments, and clauses. The keywords, statements, and clauses are
combined to enable users to create queries that extract mean-
ingful data from the database. A query is a question or command
posed to the database, and keywords are reserved words used
within queries and SQL statements. Keywords are considered
reserved because they cannot be used to name parts of the
database. For example, you cannot use a keyword to name the
database, tables, columns, or any other portion of the database.
Statements combine keywords with data to form a database
query, and a clause is a segment of an SQL statement. Since
you cannot have an actual conversation with the database like
you would a person, keywords, statements, and clauses help
you convey what you need to accomplish. Within the next few
chapters, you will learn how to implement keywords, state-
ments, and clauses in Microsoft Access.
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Structured Query Language and Microsoft Access
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