Test for numeric value?

Question

The vendor data we load in our staging table is rather dirty. One column in particular captures number data but 40% of the time has garbage characters or random strings.

Answer 1

A fairly reliable (but somewhat hackish) way is to compare the string to its upper- and lower-case self (numbers don't have different cases). As long as your data that is bringing in characters only includes Latin characters, you should be fine:

SELECT input, CASE
    WHEN UPPER(input) = LOWER(input) THEN TO_NUMBER(input)
    ELSE 0
END AS output
FROM source

Another option would be to use the TRANSLATE function:

SELECT input,
    CASE 
        WHEN TRANSLATE(CAST(input as CHAR(10)), '~~~~~~~~~~~~~', '0123456789-. ') = '~~~~~~~~~~' THEN CAST(input AS DECIMAL(12, 2))
        ELSE 0
    END AS num
FROM x