mysql prepared statement : Update query

Question

I am trying to execute a C program, using mysql C API, connecting to mysql with an update query and I am not getting any compilation or linking errors , but rows are not getting updated in the db table.

When I run this code I am getting empty values updated in emp. status field

#define STRING_SIZE 256

char* eStatus,myeStatus;

int myempid,empid;


int i;
for(i = 0; i < 5 ; i++){
const char* sqlQuery = "update employee_info set estatus = ? where empID = ?";
    if (mysql_stmt_prepare(stmt, sqlQuery, strlen(sqlQuery))) {
            fprintf(stderr, " mysql_stmt_prepare(), update failed\n");
            fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
            return -1;
          }

memset(param, 0, sizeof(param)); /* zero the structures */

if (info.state == 2)

      eStatus = "present";

else
      eStatus = "absent";

empid = i;
// Init param structure
            // Select
            param[0].buffer_type = MYSQL_TYPE_STRING;
            param[0].buffer = (void *) &eStatus;
            param[0].buffer_length = STRING_SIZE;
            param[0].is_null = 0;
            param[0].length = &str_length;

            param[1].buffer_type = MYSQL_TYPE_SHORT;
            param[1].buffer = (void *) &myempID;
            param[1].buffer_length = STRING_SIZE;

            param[1].is_null = 0;
            param[1].length = 0;

        myeStatus = eStatus;
    myempid = empid;
               if (mysql_stmt_bind_param(stmt, param) != 0) {
            fprintf(stderr, " mysql_stmt_bind_param() failed\n");
            fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
            return -1;
        }
               /* Execute the statement */
        if (mysql_stmt_execute(stmt)) {
            fprintf(stderr, " mysql_stmt_execute(), failed\n");
            fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
                return -1;
        }

} // end of for loop

Table schema in mysql

empid INT(11)

estatus varchar(10)

I am not able to figure out why status is not getting updated in mysql table. Is it a mismatch of datatypes, or values are not binded properly to sqlquery?
Any clue? Thanks.

Answer 1

You can find here : Writing into mysql database from a single board computer using c a complete example on how to use MYSQL C API to perform queries, if you still have some trouble, please post the whole code.