Column name. The column name whose value from the prior row is to be returned.
Offset. The number of rows preceding the current row from which the data is to be retrieved. For example, an offset of "1" accesses the previous row, and an offset of "3" accesses the row that is three rows before the current row.
Default. The default value to be returned if the offset is outside the scope of the partition. If you do not specify a default, the default is NULL.