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<TITLE>Connecting </TITLE>
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   <TD colspan="3" class="big">Connecting to a Datasource</TD>
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  <TD colspan="3"><P>First thing you will need is a variable of type <CODE>SQLHENV</CODE>. This is
  a handle (pointer) to an internal ODBC structure which holds all informationen about the
  ODBC environment. Without a handle of that kind you won't be able do to very much.
  To get this handle you call <CODE><A HREF="gloss.html#alloc">SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &amp;V_OD_Env)</A></CODE>.
  <CODE>V_OD_Erg</CODE> is a variable of type <CODE>SQLHENV</CODE> which holds the allocated environment handle.</P>
  <P>
  If you have allocated the handle you need to define which version of ODBC to use. Therefore 
  you should call <CODE><A HREF="gloss.html#envattr">SQLSetEnvAttr(V_OD_Env, SQL_ATTR_ODBC_VERSION, (void*)SQL_OV_ODBC3, 0)</A></CODE>.
  The constant <CODE>SQL_ATTR_ODBC_VERSION</CODE> defines that the needed version of ODBC will be defined
  and <CODE>SQL_OV_ODBC3</CODE> says that the program will need ODBC 3.0.
  </P>
  <P>Next thing to do is to create a handle for the database connection which is of the type <CODE>SQLHDBC</CODE>. Once again you call
  <CODE>SQLAllocHandle</CODE> this time with <CODE>SQL_HANDLE_DBC</CODE> and the variable to the environment returned by the first call to
  <CODE>SQLAllocHandle</CODE>.
  </P><P>
  Then you may choose to modify the connection attributes, mainly the timeout for any given
  action on the connection. You do this by calling <CODE><A HREF="gloss.html#conattr">SQLSetConnectAttr</A></CODE>
  with the connection handle, attribute and value pointer and the string length (if available).</P>
  <P>
  Finally we are able to connect to the database via <CODE><A href="gloss.html#conn">SQLConnect</A></CODE>, which needs the name of the data source,
  the username and password as parameters. For each parameter you need to specify how long the string is or just gib <COde>SQL_NTS</CODE> which
  says that it is a string which length has to be determined by <CODE>SQLConnect</CODE>
  </P>
  That's it, we are connected to the database. Please note, that all functions mentioned on this page return either <CODE>SQL_SUCCESS</CODE>, <CODE>SQL_SUCCESS_WITH_INFO</CODE> 
  if all went smoothly or <CODE>SQL_ERROR</CODE> or <CODE>SQL_INVALID_HANDLE</CODE> in case of an error. We will have a look on how to get diagnostic messages a little later.
  <P>
  So let's have a look at the code:
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  <PRE><CODE class="list">
<A NAME="list"></A>  
/* odbc.c

    testing unixODBC
*/
#include &lt;stdlib.h&gt;
#include &lt;stdio.h&gt;
#include &lt;odbc/sql.h&gt;
#include &lt;odbc/sqlext.h&gt;
#include &lt;odbc/sqltypes.h&gt;

SQLHENV			 V_OD_Env;     <FONT COLOR="green">// Handle ODBC environment</FONT>
long			 V_OD_erg;     <FONT COLOR="green">// result of functions</FONT>
SQLHDBC			 V_OD_hdbc;    <FONT COLOR="green">// Handle connection</FONT>

char			 V_OD_stat[10]; <FONT COLOR="green">// Status SQL</FONT>
SQLINTEGER		 V_OD_err,V_OD_rowanz,V_OD_id;
SQLSMALLINT		 V_OD_mlen;
char             V_OD_msg[200],V_OD_buffer[200];


int main(int argc,char *argv[])
{
	<FONT COLOR="green">// 1. allocate Environment handle and register version </FONT>
	V_OD_erg=SQLAllocHandle(SQL_HANDLE_ENV,SQL_NULL_HANDLE,&V_OD_Env);
	if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))
	{
		printf("Error AllocHandle\n");
		exit(0);
	}
	V_OD_erg=SQLSetEnvAttr(V_OD_Env, SQL_ATTR_ODBC_VERSION, 
                               (void*)SQL_OV_ODBC3, 0); 
	if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))
	{
		printf("Error SetEnv\n");
		SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
		exit(0);
	}
	<FONT COLOR="green">// 2. allocate connection handle, set timeout</FONT>
	V_OD_erg = SQLAllocHandle(SQL_HANDLE_DBC, V_OD_Env, &V_OD_hdbc); 
	if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))
	{
		printf("Error AllocHDB %d\n",V_OD_erg);
		SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
		exit(0);
	}
	SQLSetConnectAttr(V_OD_hdbc, SQL_LOGIN_TIMEOUT, (SQLPOINTER *)5, 0);
	<FONT COLOR="green">// 3. Connect to the datasource "web" </FONT>
	V_OD_erg = SQLConnect(V_OD_hdbc, (SQLCHAR*) "web", SQL_NTS,
                                     (SQLCHAR*) "christa", SQL_NTS,
                                     (SQLCHAR*) "", SQL_NTS);
	if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))
	{
		printf("Error SQLConnect %d\n",V_OD_erg);
		SQLGetDiagRec(SQL_HANDLE_DBC, V_OD_hdbc,1, 
		              V_OD_stat, &V_OD_err,V_OD_msg,100,&V_OD_mlen);
		printf("%s (%d)\n",V_OD_msg,V_OD_err);
		SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
		exit(0);
	}
	printf("Connected !\n");
	<FONT COLOR="green">/* continued on next page */</FONT>
  </CODE>
  </PRE>
  </TD>
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Name	Size	Last Modified	Owner	Permissions
close.html	1.441 KB	January 06 2014 9:37:01	root	0644
conne.html	4.916 KB	January 06 2014 9:37:01	root	0644
dsn.html	2.59 KB	January 06 2014 9:37:01	root	0644
gloss.html	19.643 KB	January 06 2014 9:37:01	root	0644
index.html	0.271 KB	January 06 2014 9:37:01	root	0644
intro.html	2.318 KB	January 06 2014 9:37:01	root	0644
navi.html	0.999 KB	January 06 2014 9:37:01	root	0644
odbc.css	6.642 KB	January 06 2014 9:37:01	root	0755
query.html	3.516 KB	January 06 2014 9:37:01	root	0644
resul.html	6.793 KB	January 06 2014 9:37:01	root	0644

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