You could also add the row in the SQL query. SELECT MAX (TimeStamp) TimeStamp, COUNT (*) RowCount FROM ... And check RowCount first. Second suggestion worked! The first suggesiton didn't work because ...

constant is a number or a quoted character string (or other special notation) that indicates a fixed value. Constants are also called literals. query-expression is described in query-expression.

The EXISTS condition is an operator whose right operand is a subquery. The result of an EXISTS condition is true if the subquery resolves to at least one row. The result of a NOT EXISTS condition is ...