5.4.22 mysql_fetch_row()

MYSQL_ROW
mysql_fetch_row(MYSQL_RES *result)

Description

Note

mysql_fetch_row() is a synchronous function. Its asynchronous counterpart is mysql_fetch_row_nonblocking(), for use by applications that require asynchronous communication with the server. See Chapter 7, C API Asynchronous Interface.

mysql_fetch_row() retrieves the next row of a result set:

• When used after mysql_store_result() or mysql_store_result_nonblocking(), mysql_fetch_row() returns NULL if there are no more rows to retrieve.

• When used after mysql_use_result(), mysql_fetch_row() returns NULL if there are no more rows to retrieve or an error occurred.

The number of values in the row is given by mysql_num_fields(result). If row holds the return value from a call to mysql_fetch_row(), pointers to the values are accessed as row[0] to row[mysql_num_fields(result)-1]. NULL values in the row are indicated by NULL pointers.

The lengths of the field values in the row may be obtained by calling mysql_fetch_lengths(). Empty fields and fields containing NULL both have length 0; you can distinguish these by checking the pointer for the field value. If the pointer is NULL, the field is NULL; otherwise, the field is empty.

Return Values

A MYSQL_ROW structure for the next row, or NULL. The meaning of a NULL return depends on which function was called preceding mysql_fetch_row():

• When used after mysql_store_result() or mysql_store_result_nonblocking(), mysql_fetch_row() returns NULL if there are no more rows to retrieve.

• When used after mysql_use_result(), mysql_fetch_row() returns NULL if there are no more rows to retrieve or an error occurred. To determine whether an error occurred, check whether mysql_error() returns a nonempty string or mysql_errno() returns nonzero.

Errors

Errors are not reset between calls to mysql_fetch_row()

• CR_SERVER_LOST

  The connection to the server was lost during the query.

• CR_UNKNOWN_ERROR

  An unknown error occurred.

Example

MYSQL_ROW row;
unsigned int num_fields;
unsigned int i;

num_fields = mysql_num_fields(result);
while ((row = mysql_fetch_row(result)))
{
   unsigned long *lengths;
   lengths = mysql_fetch_lengths(result);
   for(i = 0; i < num_fields; i++)
   {
       printf("[%.*s] ", (int) lengths[i],
              row[i] ? row[i] : "NULL");
   }
   printf("\n");
}