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PostgreSQL documentation

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ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ * ]

ALTER [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> { SET DEFAULT <replaceable

class="PARAMETER">value</replaceable> | DROP DEFAULT }

ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ * ]

ALTER [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> { SET | DROP } NOT NULL

ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ * ]

ALTER [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> SET STATISTICS <replaceable class="PARAMETER">integer</replaceable>

ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ * ]

allow you to set or remove the default for the column. Note that defaults

only apply to subsequent <command>INSERT</command> commands; they do not

cause rows already in the table to change.

The <literal>ALTER COLUMN SET/DROP NOT NULL</literal> forms allow you to

change whether a column is marked to allow NULL values or to reject NULL

values.

The <literal>ALTER COLUMN SET STATISTICS</literal> form allows you to

set the statistics-gathering target for subsequent

<xref linkend="sql-analyze" endterm="sql-analyze-title"> operations.

</programlisting>

</para>

<para>

To add a NOT NULL constraint to a column:

<programlisting>

ALTER TABLE distributors ALTER COLUMN street SET NOT NULL;

</programlisting>

To remove a NOT NULL constraint from a column:

<programlisting>

ALTER TABLE distributors ALTER COLUMN street DROP NOT NULL;

</programlisting>

</para>

<para>

To add a check constraint to a table:

<programlisting>

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<appendix id="release">

worries about funny characters.

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<literallayout><![CDATA[

ALTER TABLE ALTER COLUMN SET/DROP NOT NULL

EXPLAIN output comes out as a query result, not a NOTICE message

DOMAINs (types that are constrained versions of base types)

Access privileges on functions