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<title>OTL 4.0, Example 145 (otl_stream::describe_select() with a
simple Select)</title>
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<h1>OTL 4.0, Example 145<br>
(otl_stream::describe_select() with a simple Select)</h1>
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<h1>
Example 145 (otl_stream::describe_select() with a simple Select)</h1>
This example demonstrates the <a
href="otl3_stream_class.htm#describe_select">otl_stream::describe_select</a>()
with a simple SELECT statement.
<h2>Source Code</h2>
<pre>#include <iostream><br>using namespace std;<br><br>#include <stdio.h></pre>
<pre>// #define OTL_ODBC_UNIX // uncomment this line if UnixODBC is used<br>#if !defined(_WINDOWS_) && !defined(_WIN64)<br>#define <a
href="otl3_compile.htm#OTL_ODBC">OTL_ODBC</a><br>#else <br>#define <a
href="otl3_compile.htm#OTL_ODBC_POSTGRESQL">OTL_ODBC_POSTGRESQL</a> // required with PG ODBC on Windows<br>#endif<br>#include <otlv4.h> // include the OTL 4.0 header file<br><br><br><a
href="otl3_connect_class.htm">otl_connect</a> db; // connect object<br><br>void select()<br>{ <br> <a
href="otl3_stream_class.htm">otl_stream</a> i(10, // buffer size<br> "select * from test_tab",<br> // SELECT statement<br> db // connect object<br> ); <br> // create select stream<br> <br> <a
href="otl3_stream_class.htm#otl_column_desc">otl_column_desc</a>* desc;<br> int desc_len;<br><br> desc=i.<a
href="otl3_stream_class.htm#describe_select">describe_select</a>(desc_len);<br><br> for(int n=0;n<desc_len;++n){<br> cout<<"========== COLUMN #"<<n+1<<" ==========="<<endl;<br> cout<<"name="<<desc[n].name<<endl;<br> cout<<"dbtype="<<desc[n].dbtype<<endl;<br> cout<<"<a
href="otl3_stream_class.htm#otl_var_dbtype">otl_var_dbtype</a>="<<desc[n].otl_var_dbtype<<endl;<br> cout<<"dbsize="<<desc[n].dbsize<<endl;<br> cout<<"scale="<<desc[n].scale<<endl;<br> cout<<"prec="<<desc[n].prec<<endl;<br> cout<<"nullok="<<desc[n].nullok<<endl;<br> }<br> <br>}<br><br>int main()<br>{<br> <a
href="otl3_connect_class.htm">otl_connect::otl_initialize</a>(); // initialize ODBC environment<br> try{<br><br> db.rlogon("UID=scott;PWD=tiger;DSN=postgresql"); // connect to ODBC<br>// db.rlogon("scott/tiger@postgresql"); // connect to ODBC, alternative format<br> // of connect string<br> <a
href="otl3_const_sql.htm">otl_cursor::direct_exec<br></a> (<br> db,<br> "drop table test_tab",<br> otl_exception::disabled // disable OTL exceptions<br> ); // drop table<br><br> db.commit();<br><br> <a
href="otl3_const_sql.htm">otl_cursor::direct_exec<br></a> (<br> db,<br> "create table test_tab(f1 int, f2 varchar(30), f3 timestamp, f4 text)"<br> ); // create table<br><br> db.commit(); // committing the create table statement to to the database<br><br> select(); // select records from table<br><br> }<br><br> catch(<a
href="otl3_exception_class.htm">otl_exception</a>& p){ // intercept OTL exceptions<br> cerr<<p.msg<<endl; // print out error message<br> cerr<<p.stm_text<<endl; // print out SQL that caused the error<br> cerr<<p.var_info<<endl; // print out the variable that caused the error<br> }<br><br> db.logoff(); // disconnect from ODBC<br><br> return 0;<br><br>}</pre>
<h2>
Output</h2>
<pre>========== COLUMN #1 ===========<br>name=f1<br>dbtype=4<br>otl_var_dbtype=4<br>dbsize=10<br>scale=0<br>prec=10<br>nullok=1<br>========== COLUMN #2 ===========<br>name=f2<br>dbtype=12<br>otl_var_dbtype=1<br>dbsize=30<br>scale=0<br>prec=30<br>nullok=1<br>========== COLUMN #3 ===========<br>name=f3<br>dbtype=93<br>otl_var_dbtype=8<br>dbsize=21<br>scale=0<br>prec=21<br>nullok=1<br>========== COLUMN #4 ===========<br>name=f4<br>dbtype=-1<br>otl_var_dbtype=9<br>dbsize=8190<br>scale=0<br>prec=8190<br>nullok=1<br><br><br><hr
width="100%"></pre>
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