-3021: Invalid mixture of functions and columns 

Explanation:

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       1.      If a set function (AVG, COUNT, MAX, MIN, STDDEV, SUM, VARIANCE) occurs in a SELECT statement, non-group columns are not allowed in the selected columns (select_column).

       2.      Quantity functions, e.g. AVG (SUM...), must not be nested.

       3.      A corresponding subquery S contained in the WHERE clause of the QUERY specification Q must not contain quantity functions for columns of tables specified in the FROM clause of the QUERY specification Q.

User Action:

Correct the SQL statement.

Try to achieve the desired effect without nesting the quantity functions by using several QUERY statements, each containing a quantity function.

Within a QUERY statement, the effect can be achieved by specifying a QUERY expression in the FROM clause.