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<chapter id="ddl">

<title>Data Definition</title>

A table in a relational database is much like a table on paper: It

consists of rows and columns. The number and order of the columns

is fixed, and each column has a name. The number of rows is

variable-- it reflects how much data is stored at a given moment.

variable&mdash; it reflects how much data is stored at a given moment.

SQL does not make any guarantees about the order of the rows in a

table. When a table is read, the rows will appear in random order,

unless sorting is explicitly requested. This is covered in <xref