Empty Cells

Usually cubes have empty data points (cells). For example (using SalesCube from the cube and dataset example), the SalesPerson “Venkatrao” sells products only in the USA, so the point corresponding to the coordinates (Venkatrao, Canada, Years.All, Quarters.All, Sales) has no data. In fact, no point has data whose coordinates are (Venkatrao, Geography.x, Years.any, Quarters.<any>, Sales), where x <> “USA” and any represents any member of a dimension.

Empty cells affect the evaluation of value expressions and search conditions. To see why this is so, note that a value expression is composed of value expression primaries. One of the value expression primaries is tuple[.VALUE], which returns the value of a cell in the cube (some of whose coordinates are specified explicitly by tuple, and others are available implicitly from the context of the MDX expression). This cell can be an empty cell. There are three cases where the empty cells affect expression evaluation:

• In a numeric value expression, this value can be added, subtracted, multiplied, or divided by other values. It can also appear as the parameter of any function that has a numeric_value_expression argument.
  
  
• In a string value expression, this value can be concatenated to another string.
  
  
• A search condition is composed of Boolean primaries. A Boolean primary is of the form:

  <boolean_primary> ::= <value_expression> <comp_op> <value_expression>
  

A value expression will be made up of the value expression primary and this will lead to the first two cases described above.