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><H1
><A
NAME="SQL-TRUNCATE"
></A
>TRUNCATE</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN54914"
></A
><H2
>Name</H2
>TRUNCATE -- empty a table or set of tables</DIV
><A
NAME="AEN54917"
></A
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN54919"
></A
><H2
>Synopsis</H2
><PRE
CLASS="SYNOPSIS"
>TRUNCATE [ TABLE ] <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
> [, ...] [ CASCADE | RESTRICT ]</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN54922"
></A
><H2
>Description</H2
><P
> <TT
CLASS="COMMAND"
>TRUNCATE</TT
> quickly removes all rows from a set of
tables. It has the same effect as an unqualified
<TT
CLASS="COMMAND"
>DELETE</TT
> on each table, but since it does not actually
scan the tables it is faster. This is most useful on large tables.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN54927"
></A
><H2
>Parameters</H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
></DT
><DD
><P
> The name (optionally schema-qualified) of a table to be truncated.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>CASCADE</TT
></DT
><DD
><P
> Automatically truncate all tables that have foreign-key references
to any of the named tables, or to any tables added to the group
due to <TT
CLASS="LITERAL"
>CASCADE</TT
>.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>RESTRICT</TT
></DT
><DD
><P
> Refuse to truncate if any of the tables have foreign-key references
from tables that are not to be truncated. This is the default.
</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN54946"
></A
><H2
>Notes</H2
><P
> Only the owner of a table may <TT
CLASS="COMMAND"
>TRUNCATE</TT
> it.
</P
><P
> <TT
CLASS="COMMAND"
>TRUNCATE</TT
> cannot be used on a table that has foreign-key
references from other tables, unless all such tables are also truncated
in the same command. Checking validity in such cases would require table
scans, and the whole point is not to do one. The <TT
CLASS="LITERAL"
>CASCADE</TT
>
option can be used to automatically include all dependent tables —
but be very careful when using this option, else you might lose data you
did not intend to!
</P
><P
> <TT
CLASS="COMMAND"
>TRUNCATE</TT
> will not run any user-defined <TT
CLASS="LITERAL"
>ON
DELETE</TT
> triggers that might exist for the tables.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN54956"
></A
><H2
>Examples</H2
><P
> Truncate the tables <TT
CLASS="LITERAL"
>bigtable</TT
> and <TT
CLASS="LITERAL"
>fattable</TT
>:
</P><PRE
CLASS="PROGRAMLISTING"
>TRUNCATE TABLE bigtable, fattable;</PRE
><P>
</P
><P
> Truncate the table <TT
CLASS="LITERAL"
>othertable</TT
>, and cascade to any tables
that are referencing <TT
CLASS="LITERAL"
>othertable</TT
> via foreign-key
constraints:
</P><PRE
CLASS="PROGRAMLISTING"
>TRUNCATE othertable CASCADE;</PRE
><P>
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN54966"
></A
><H2
>Compatibility</H2
><P
> There is no <TT
CLASS="COMMAND"
>TRUNCATE</TT
> command in the SQL standard.
</P
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>
distrib
>
Mandriva
>
2010.0
>
i586
>
media
>
contrib-release
>
by-pkgid
>
a866202fe868538f89a755dbcabc378b
>
files
>
736
