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<chapter id="ddl">

<title>Data Definition</title>

</para>

<para>

Check constraints can be defined on tables within an inheritance

hierarchy. All check constraints on a parent table are

automatically inherited by all of its children. Other types of

constraints are not inherited, however.

All check constraints and not-null constraints on a parent table are

automatically inherited by its children. Other types of constraints

(unique, primary key, and foreign key constraints) are not inherited.

</para>

<para>

so that there is only one such column in the child table. To be merged,

columns must have the same data types, else an error is raised. The

merged column will have copies of all the check constraints coming from

any one of the column definitions it came from.

any one of the column definitions it came from, and will be marked not-null

if any of them are.

</para>

<para>