A slicer axis is a way to limit a query to apply to only a specific area of the database. The optional slicer, if used, must be in the WHERE section of an MDX query. Furthermore, the WHERE section must be the last component of the query, following the cube specification (the FROM section):
SELECT {set} ON axes FROM database WHERE slicer
Use the slicer axis to set the context of the query; it is usually the default context for all the other axes.
For example, for a query to select only Actual Sales in the Sample.Basic database, excluding budgeted sales, the WHERE clause might look like the following:
WHERE ([Actual], [Sales])
Because (Actual, Sales) is specified in the slicer axis, you need not include them in the ON AXIS(n) set specifications.