If the execution of the statement went fine you are now able to fetch
the data column by column. May be you would first like to know
how many columns there are in the result set (if you use a SELECT * FROM tkeyuser
you wouldn't know in your program). A call to SQLNumResultCols.
This function takes the statement handle and a pointer to an integer variable which will yield the
number of columns after the call.
Knowing that much we can add this to our program:
// At the beginning add:
SQLSMALLINT V_OD_colanz; // Num of columns
// At the end add:
V_OD_erg=SQLNumResultCols(V_OD_hstmt,&V_OD_colanz);
if ((V_OD_erg != SQL_SUCCESS) &&
(V_OD_erg != SQL_SUCCESS_WITH_INFO))
{
printf("Fehler im ResultCols %d\n",V_OD_erg);
SQLFreeHandle(SQL_HANDLE_STMT,V_OD_hstmt);
SQLFreeHandle(SQL_HANDLE_DBC,V_OD_hdbc);
SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
exit(0);
}
printf("Number of Columns %d\n",V_OD_colanz);
The next thing you need to know is how many rows have
been returned by the query. A call to SQLRowCount should
quench your thirst for knowledge.
The last thing to do is to fetch the data itself from the result set. You should call SQLFetch
with a statement handle (which has been allocated and SQLBind has been called for all columns).
SQLFetch returns SQL_NO_DATA if there is no more data in the result set.
So here is the complete source code. Real C-programmers will moan in disgust
how inefficient the program is coded, but I prefer it that way (doesn't it look a little bit like PASCAL?).
Take it as a starting point for your own endeavors with ODBC.
/* odbc.c
testing unixODBC
*/
#include <stdlib.h>
#include <stdio.h>
#include <odbc/sql.h>
#include <odbc/sqlext.h>
#include <odbc/sqltypes.h>
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,V_OD_colanz;
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");
V_OD_erg=SQLAllocHandle(SQL_HANDLE_STMT, V_OD_hdbc, &V_OD_hstmt);
if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))
{
printf("Fehler im AllocStatement %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);
}
SQLBindCol(V_OD_hstmt,1,SQL_C_CHAR, &V_OD_buffer,150,&V_OD_err);
SQLBindCol(V_OD_hstmt,2,SQL_C_ULONG,&V_OD_id,150,&V_OD_err);
V_OD_erg=SQLExecDirect(V_OD_hstmt,"SELECT dtname,iduser FROM tkeyuser order by iduser",SQL_NTS);
if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))
{
printf("Error in Select %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_STMT,V_OD_hstmt);
SQLFreeHandle(SQL_HANDLE_DBC,V_OD_hdbc);
SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
exit(0);
}
V_OD_erg=SQLNumResultCols(V_OD_hstmt,&V_OD_colanz);
if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))
{
SQLFreeHandle(SQL_HANDLE_STMT,V_OD_hstmt);
SQLDisconnect(V_OD_hdbc);
SQLFreeHandle(SQL_HANDLE_DBC,V_OD_hdbc);
SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
exit(0);
}
printf("Number of Columns %d\n",V_OD_colanz);
V_OD_erg=SQLRowCount(V_OD_hstmt,&V_OD_rowanz);
if ((V_OD_erg != SQL_SUCCESS) && (V_OD_erg != SQL_SUCCESS_WITH_INFO))
{
printf("Number ofRowCount %d\n",V_OD_erg);
SQLFreeHandle(SQL_HANDLE_STMT,V_OD_hstmt);
SQLDisconnect(V_OD_hdbc);
SQLFreeHandle(SQL_HANDLE_DBC,V_OD_hdbc);
SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
exit(0);
}
printf("Number of Rows %d\n",V_OD_rowanz);
V_OD_erg=SQLFetch(V_OD_hstmt);
while(V_OD_erg != SQL_NO_DATA)
{
printf("Result: %d %s\n",V_OD_id,V_OD_buffer);
V_OD_erg=SQLFetch(V_OD_hstmt);
} ;
SQLFreeHandle(SQL_HANDLE_STMT,V_OD_hstmt);
SQLDisconnect(V_OD_hdbc);
SQLFreeHandle(SQL_HANDLE_DBC,V_OD_hdbc);
SQLFreeHandle(SQL_HANDLE_ENV, V_OD_Env);
return(0);
}
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