title: How do I filter out NaN FLOAT values in Teradata SQL?
body: <p>With the Teradata database, it is possible to load values of NaN, -Inf, and +Inf into FLOAT columns through Java.  Unfortunately, once those values get into the tables, they make life difficult when writing SQL that needs to filter them out.  There is no IsNaN() function, nor can you "CAST ('NaN' as FLOAT)" and use an equality comparison.</p>
  
  <p>What I would like to do is,</p>
  
  <pre><code>SELECT
    SUM(VAL**2)
  FROM
    DTM
  WHERE
    NOT ABS(VAL) &gt; 1e+21 AND
    NOT VAL = CAST ('NaN' AS FLOAT)
  </code></pre>
  
  <p>but that fails with error 2620, "The format or data contains a bad character.", specifically on the CAST.  I've tried simply "... AND NOT VAL = 'NaN'", which also fails for a similar reason (3535, "A character string failed conversion to a numeric value.").  I cannot seem to figure out how to represent NaN within the SQL statement.  Even if I could represent NaN successfully in an SQL statement, I would be concerned that the comparison would fail.  According to the IEEE 754 spec, NaN = NaN should evaluate to false. What I really seem to need is an IsNaN() function.  Yet that function does not seem to exist.</p>