Order of fields in a table

           Efficient method for the order of fields in a table :
           
           I am trying to determine an efficient method for storing 
           fields in a table. The ordering of fields can improve the 
           performance of a query, especially when massive reads are 
           done. 
           
           Does anyone have any knowledge on how Oracle expands a 
           record ?
           
           The worst case scenario is that for every record retrieved, 
           Oracle will expand the entire record and determine the 
           value of every column.
           
           The best case scenario is that Oracle will only expand the 
           record until it has retrieved the columns that it needs. If 
           it is accessing the table through an index then it will not 
           extract from the table the indexed column.
           
           I am aware that fields which are not null should be 
           separated from null fields, to improve the efficiency of 
           the compression algorithm and that the most frequently used 
           fields should be at the beginning of the table. Also that 
           if a LONG field is used, it should be the last column in 
           the table.
           
           I will summarise all responses sent to me.
           
           Marcel K.
           Database Administration.
           
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