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<title>OTL 4.0, Example 283 (otl_stream and NULLs)</title>
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<h1>OTL 4.0, Example 283 (otl_stream and NULLs)</h1>
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<h1>
Example 283 (otl_stream and NULLs)</h1>
This example demonstrates the otl_stream with NULLs.
<h2>Source Code</h2>
<pre>#include <iostream><br>using namespace std;<br><br>#include <stdio.h></pre>
<pre>#define <a href="otl3_compile.htm#OTL_ODBC">OTL_ODBC</a> // Compile OTL 4.0/ODBC<br>#define ODBCVER 0x0250 // ODBC Version # needs to be downgraded<br> // to 2.5 because the SQLite ODBC driver is<br> // not up to the ODBC 3.5 level just yet<br><br>// #define OTL_ODBC_UNIX // uncomment this line if UnixODBC is used<br>#include <otlv4.h> // include the OTL 4.0 header file<br><br><a
href="otl3_connect_class.htm">otl_connect</a> db; // connect object<br><br>void insert()<br>// insert rows into table<br>{ <br> // open a stream with no implicit committing<br> <a
href="otl3_stream_class.htm#no_commit">otl_nocommit_stream</a> o<br> (50, // buffer size<br> "insert into test_tab values(:f1<float>,:f2<char[31]>)", <br> // SQL statement<br> db // connect object<br> );<br> char tmp[32];<br><br> <a
href="otl3_const_sql.htm">otl_cursor::direct_exec</a>(db,"BEGIN TRANSACTION");<br> // begin transaction. This explicit construct needs to be used <br> // because the ODBC driver could eventually run into the <br> // "Function Sequence Error" error.<br><br> for(int i=1;i<=100;++i){<br> sprintf(tmp,"Name%d",i);<br> if(i==10)<br> o<<(float)i<<<a
href="otl3_stream_class.htm#otl_null">otl_null</a>();<br> else<br> o<<(float)i<<tmp;<br> }<br> o.<a
href="otl3_stream_class.htm#flush">flush</a>(); // flush the stream buffer to make sure that <br> // all rows get to the table<br> <a
href="otl3_const_sql.htm">otl_cursor::direct_exec</a>(db,"COMMIT TRANSACTION");<br> // commit transaction<br><br>}<br><br>void select()<br>{ <br> <a
href="otl3_stream_class.htm">otl_stream</a> i(50, // buffer size<br> "select * from test_tab where f1>=:f11<int> and f1<=:f12<int>*2",<br> // SELECT statement<br> db // connect object<br> ); <br> // create select stream<br> <br> float f1;<br> char f2[31];<br><br> i<<8<<8; // assigning :f11 = 8, :f12=8<br> // SELECT automatically executes when all input variables are<br> // assigned. First portion of output rows is fetched to the buffer<br><br> while(!i.eof()){ // while not end-of-data<br> i>>f1;<br> if(i.is_null())<br> cout<<"f1=NULL,";<br> else<br> cout<<"f1="<<f1<<",";<br> i>>f2;<br> if(i.is_null())<br> cout<<"f2=NULL";<br> else<br> cout<<"f2="<<f2;<br> cout<<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("scott/tiger@sqlite",1); <br> // connect to the database and set the auto-commit to on. <br> // The auto-commit is needed to make "BEGIN TRANSACTION" / <br> // "COMMIT TRANSACTION" work properly.<br><br><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> <a
href="otl3_const_sql.htm">otl_cursor::direct_exec<br></a> (<br> db,<br> "create table test_tab(f1 int, f2 varchar(30))"<br> ); // create table<br><br> insert(); // insert records into table<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.sqlstate<<endl; // print out SQLSTATE message<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>f1=8, f2=Name8<br>f1=9, f2=Name9<br>f1=10, f2=NULL<br>f1=11, f2=Name11<br>f1=12, f2=Name12<br>f1=13, f2=Name13<br>f1=14, f2=Name14<br>f1=15, f2=Name15<br>f1=16, f2=Name16</pre>
<pre><hr width="100%"></pre>
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