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✏️ Editing: conne.html

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 <TD colspan="3" class="big">Connecting to a Datasource</TD>
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 <TD colspan="3">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.
 
 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.
 
 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>.
 
 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).
 
 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>
 
 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.
 
 So let's have a look at the code:
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/* 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; // Handle ODBC environment
long			 V_OD_erg; // result of functions
SQLHDBC			 V_OD_hdbc; // Handle connection

char			 V_OD_stat[10]; // Status SQL
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[])
{
	// 1. allocate Environment handle and register version 
	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);
	}
	// 2. allocate connection handle, set timeout
	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);
	// 3. Connect to the datasource "web" 
	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");
	/* continued on next page */
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MR SKB