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diff --git a/doc/src/sgml/html/ecpg-sql-get-descriptor.html b/doc/src/sgml/html/ecpg-sql-get-descriptor.html new file mode 100644 index 0000000..3cfb91f --- /dev/null +++ b/doc/src/sgml/html/ecpg-sql-get-descriptor.html @@ -0,0 +1,104 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>GET DESCRIPTOR</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="ecpg-sql-execute-immediate.html" title="EXECUTE IMMEDIATE" /><link rel="next" href="ecpg-sql-open.html" title="OPEN" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">GET DESCRIPTOR</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="ecpg-sql-execute-immediate.html" title="EXECUTE IMMEDIATE">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="ecpg-sql-commands.html" title="36.14. 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Embedded SQL Commands</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="ecpg-sql-open.html" title="OPEN">Next</a></td></tr></table><hr /></div><div class="refentry" id="ECPG-SQL-GET-DESCRIPTOR"><div class="titlepage"></div><div class="refnamediv"><h2>GET DESCRIPTOR</h2><p>GET DESCRIPTOR — get information from an SQL descriptor area</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis"> +GET DESCRIPTOR <em class="replaceable"><code>descriptor_name</code></em> <em class="replaceable"><code>:cvariable</code></em> = <em class="replaceable"><code>descriptor_header_item</code></em> [, ... ] +GET DESCRIPTOR <em class="replaceable"><code>descriptor_name</code></em> VALUE <em class="replaceable"><code>column_number</code></em> <em class="replaceable"><code>:cvariable</code></em> = <em class="replaceable"><code>descriptor_item</code></em> [, ... ] +</pre></div><div class="refsect1" id="id-1.7.5.20.11.3"><h2>Description</h2><p> + <code class="command">GET DESCRIPTOR</code> retrieves information about a + query result set from an SQL descriptor area and stores it into + host variables. A descriptor area is typically populated + using <code class="command">FETCH</code> or <code class="command">SELECT</code> + before using this command to transfer the information into host + language variables. + </p><p> + This command has two forms: The first form retrieves + descriptor <span class="quote">“<span class="quote">header</span>”</span> items, which apply to the result + set in its entirety. One example is the row count. The second + form, which requires the column number as additional parameter, + retrieves information about a particular column. Examples are + the column name and the actual column value. + </p></div><div class="refsect1" id="id-1.7.5.20.11.4"><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="replaceable"><code>descriptor_name</code></em></span></dt><dd><p> + A descriptor name. + </p></dd><dt><span class="term"><em class="replaceable"><code>descriptor_header_item</code></em></span></dt><dd><p> + A token identifying which header information item to retrieve. + Only <code class="literal">COUNT</code>, to get the number of columns in the + result set, is currently supported. + </p></dd><dt><span class="term"><em class="replaceable"><code>column_number</code></em></span></dt><dd><p> + The number of the column about which information is to be + retrieved. The count starts at 1. + </p></dd><dt><span class="term"><em class="replaceable"><code>descriptor_item</code></em></span></dt><dd><p> + A token identifying which item of information about a column + to retrieve. See <a class="xref" href="ecpg-descriptors.html#ECPG-NAMED-DESCRIPTORS" title="36.7.1. Named SQL Descriptor Areas">Section 36.7.1</a> for + a list of supported items. + </p></dd><dt><span class="term"><em class="replaceable"><code>cvariable</code></em></span></dt><dd><p> + A host variable that will receive the data retrieved from the + descriptor area. + </p></dd></dl></div></div><div class="refsect1" id="id-1.7.5.20.11.5"><h2>Examples</h2><p> + An example to retrieve the number of columns in a result set: +</p><pre class="programlisting"> +EXEC SQL GET DESCRIPTOR d :d_count = COUNT; +</pre><p> + </p><p> + An example to retrieve a data length in the first column: +</p><pre class="programlisting"> +EXEC SQL GET DESCRIPTOR d VALUE 1 :d_returned_octet_length = RETURNED_OCTET_LENGTH; +</pre><p> + </p><p> + An example to retrieve the data body of the second column as a + string: +</p><pre class="programlisting"> +EXEC SQL GET DESCRIPTOR d VALUE 2 :d_data = DATA; +</pre><p> + </p><p> + Here is an example for a whole procedure of + executing <code class="literal">SELECT current_database();</code> and showing the number of + columns, the column data length, and the column data: +</p><pre class="programlisting"> +int +main(void) +{ +EXEC SQL BEGIN DECLARE SECTION; + int d_count; + char d_data[1024]; + int d_returned_octet_length; +EXEC SQL END DECLARE SECTION; + + EXEC SQL CONNECT TO testdb AS con1 USER testuser; + EXEC SQL SELECT pg_catalog.set_config('search_path', '', false); EXEC SQL COMMIT; + EXEC SQL ALLOCATE DESCRIPTOR d; + + /* Declare, open a cursor, and assign a descriptor to the cursor */ + EXEC SQL DECLARE cur CURSOR FOR SELECT current_database(); + EXEC SQL OPEN cur; + EXEC SQL FETCH NEXT FROM cur INTO SQL DESCRIPTOR d; + + /* Get a number of total columns */ + EXEC SQL GET DESCRIPTOR d :d_count = COUNT; + printf("d_count = %d\n", d_count); + + /* Get length of a returned column */ + EXEC SQL GET DESCRIPTOR d VALUE 1 :d_returned_octet_length = RETURNED_OCTET_LENGTH; + printf("d_returned_octet_length = %d\n", d_returned_octet_length); + + /* Fetch the returned column as a string */ + EXEC SQL GET DESCRIPTOR d VALUE 1 :d_data = DATA; + printf("d_data = %s\n", d_data); + + /* Closing */ + EXEC SQL CLOSE cur; + EXEC SQL COMMIT; + + EXEC SQL DEALLOCATE DESCRIPTOR d; + EXEC SQL DISCONNECT ALL; + + return 0; +} +</pre><p> + When the example is executed, the result will look like this: +</p><pre class="screen"> +d_count = 1 +d_returned_octet_length = 6 +d_data = testdb +</pre><p> + </p></div><div class="refsect1" id="id-1.7.5.20.11.6"><h2>Compatibility</h2><p> + <code class="command">GET DESCRIPTOR</code> is specified in the SQL standard. + </p></div><div class="refsect1" id="id-1.7.5.20.11.7"><h2>See Also</h2><span class="simplelist"><a class="xref" href="ecpg-sql-allocate-descriptor.html" title="ALLOCATE DESCRIPTOR">ALLOCATE DESCRIPTOR</a>, <a class="xref" href="ecpg-sql-set-descriptor.html" title="SET DESCRIPTOR">SET DESCRIPTOR</a></span></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ecpg-sql-execute-immediate.html" title="EXECUTE IMMEDIATE">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ecpg-sql-commands.html" title="36.14. 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