Subqueries cannot be used in the expression <expression>. (Error 3203)

The specified expression contains a subquery or other expression that functions as a subquery.

Possible cause:

• You used a SELECT statement that includes an aggregate function that evaluates another aggregate function. This error occurs, for example, if you execute the following statement:

  TRANSFORM Sum([OrderAmount]) AS Sum1

  SELECT Sum([Sum1]) AS Sum2, OrderID, Sum([Sum2]) AS Expr1

  FROM Orders

  GROUP BY OrderID

  PIVOT ShipName;

  The <expression> parameter of the alert would contain the expression Sum([Sum2]) from the SELECT clause, because this references an alias used in the same SELECT statement and acts as a subquery against Sum([Sum1]).