Accessing Pervasive.SQL With Perl

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DBI + ODBC - Which Fetch?

Having executed the query and marked the selected rows for retrieval, there are various methods available in DBI to fetch the data.

1. fetchrow_array
   This retrieves one row at a time - you call it until you get undef as the return value, which indocates that there are no more rows to return.
   
   while(@returnRow = $stHandle->fetchrow_array())
   {
   # process row
   }
   
   @returnRow is an array of fields in the row,
    
2. fetchrow_arrayref/fetch
   fetch is the shorthand version of fetchrow_arrayref and is faster than fetchrow_array
   
   while($returnRowRef = $stHandle->fetch())
   {
   # process row reference
   }
   
   Instead of retrieving a new copy for each row, fetchrow_arayref returns a reference to an internal copy that is filled with the current row's data. Each call to fetch/fetchrow_arrayref populates the internal array with the next row's data and returns the reference. Again, if undef is returned there are no more rows.
    
3. fetchrow_hashref
   Instead of returning an array reference like fetchrow_arrayref, this method returns a reference to a hash, where the keys are the column names and the values are the data. We gain knowledge of the column names without having to resort to driver-specific metadata, but we lose performance.
   
   while($returnHashRef = $stHandle->fetchrow_hashref())
   {
   # process row hash reference
   }

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