MDAC 2.5 SDK - OLE DB Programmer's Reference
Chapter 26: Mapping MDX to SQL Statements

FROM Clause

In an MDX statement, the FROM clause has a cube name. In the corresponding SQL statements (there are multiple statements because multiple tables must be generated), FROM clauses will contain the MEMBERS table (for generating the axis tables) or the FACT table (for generating the VALUES table). Depending on the query, the LEVELS table might also be joined to the MEMBERS table when generating the axes tables.