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<?xml version="1.0" encoding="ISO-8859-1"?>
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- project.
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- Copyright (C) 1998-2018 OpenLink Software
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- under the terms of the GNU General Public License as published by the
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- WITHOUT ANY WARRANTY; without even the implied warranty of
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- General Public License for more details.
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- You should have received a copy of the GNU General Public License along
- with this program; if not, write to the Free Software Foundation, Inc.,
- 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
-
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-->
<!-- REMOVE FROM INDEX bug 1690 -->
<refentry id="fn_row_column">
<refmeta>
<refentrytitle>row_column</refentrytitle>
<refmiscinfo>sql</refmiscinfo>
</refmeta>
<refnamediv>
<refname>row_column</refname>
<refpurpose>Retrieves a column value from a row string given the name of
the table and column.</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis id="fsyn_row_column">
<funcprototype id="fproto_row_column">
<funcdef><function>row_column</function></funcdef>
<paramdef>in <parameter>row </parameter>varchar</paramdef>
<paramdef>in <parameter>table_name </parameter>varchar</paramdef>
<paramdef>in <parameter>col_name </parameter>varchar</paramdef>
<paramdef>out <parameter>exists </parameter>integer</paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 id="desc_row_column"><title>Description</title>
<para>
This function retrieves a column value from a row string given the name of
the table and column if such a column existed in the row. If not, NULL is
returned.
</para>
<para>
<parameter>row</parameter> is a row string obtained by selecting _ROW from
some table, or a row identity string returned by
<function>row_identity()</function>. In this case
the column being retrieved must be part of the primary key of the table
the row identity string references.
</para>
<para>
<parameter>Table_name</parameter> is the name of the table that defines the column being retrieved.
</para>
<para>
<parameter>Col_name</parameter> is the name of the column.
</para>
<para>
The output parameter <parameter>exists</parameter> is optional. If a
variable is specified here,
it is set to 1 if the table contains a column of the name requested.
</para>
<para>
If <parameter>table_name</parameter> and <parameter>col_name</parameter> specify a column that is not in the row,
NULL is returned. This can happen if the row comes from a table other than
the one specified in <parameter>table_name</parameter>.
</para>
<programlisting>
Diagnostics: OB001 Illegal row string.
</programlisting>
<example id="ex_row_column">
<!-- <title>Example:</title> -->
<programlisting>
select row_column (_ROW, 'employee', 'emp_name') from employee;
</programlisting>
<para>
is identical to
</para>
<programlisting>
select emp_name from employee;
</programlisting>
</example>
<para>
The direct column reference is faster, naturally.
</para>
</refsect1>
<refsect1 id="seealso_row_column">
<title>See Also</title>
<para>
<link linkend="fn_row_table"><function>row_table()</function></link>
<link linkend="fn_row_identity"><function>row_identity()</function></link>
<link linkend="fn__row"><function>_row()</function></link>
</para>
</refsect1>
</refentry>
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