ORACLE - Select Count on a Subquery

Question

I\'ve got an Oracle table that holds a set of ranges (RangeA and RangeB). These columns are varchar as they can hold both numeric and alphanumeric values, like the following exa

Answer 1

You can test each column with a regular expression to determine if it is a valid number:

SELECT COUNT(1)
FROM   table_of_ranges
WHERE  CASE WHEN REGEXP_LIKE( RangeA, '^-?\d+(\.\d*)?$' )
            THEN TO_NUMBER( RangeA )
            ELSE NULL END
          < 10
AND    REGEXP_LIKE( RangeB, '^-?\d+(\.\d*)?$' );

Another alternative is to use a user-defined function:

CREATE OR REPLACE FUNCTION test_Number (
  str VARCHAR2
) RETURN NUMBER DETERMINISTIC
AS
  invalid_number EXCEPTION;
  PRAGMA EXCEPTION_INIT(invalid_number, -6502);
BEGIN
  RETURN TO_NUMBER( str );
EXCEPTION
  WHEN invalid_number THEN
    RETURN NULL;
END test_Number;
/

Then you can do:

SELECT COUNT(*)
FROM   table_of_ranges
WHERE  test_number( RangeA ) <= 10
AND    test_number( RangeB ) IS NOT NULL;

Answer 2

Coming to this question almost four years later (obviously, pointed here from a much newer thread). The other answers show how to achieve the desired output, but do not answer the OP's question, which was "what am I doing wrong?"

You are not doing anything wrong. Oracle is doing something wrong. It is "pushing" the predicate (the WHERE condition) from the outer query into the inner query. Pushing predicates is one of the most basic ways in which the Optimizer makes queries more efficient, but in some cases (and the question you ask is a PERFECT illustration) the result is not, in fact, logically equivalent to the original query.

There are ways to prevent the Optimizer from pushing predicates; or you can write the query in a better way (as shown in the other answers). But if you wanted to know why you saw what you saw, this is why.

Answer 3

Try this query:

  SELECT COUNT(*)
  FROM table R
  WHERE translate(R.RangeA, 'x0123456789', 'x') = 'x' and
        translate(R.RangeB, 'x0123456789', 'x') = 'x'

First, you don't need the subquery for this purpose. Second, using to_number() or upper()/lower() are prone to other problems. The function translate() replaces each character in the second argument with values from the third argument. In this case, it removes numbers. If nothing is left over, then the original value was an integer.

You can do more sophisticated checks for negative values and floating point numbers, but the example in the question seemed to be about positive integer values.