## -3021: Invalid mixture of functions and columns

### Explanation:

...

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.