If I understand your question correctly you are looking for a character value for the number that is inside the CHAR parentheses?
To do that you would need to use the rex I mentioned earlier to get it as a field and then use a lookup table to find the resulting translation. Splunk doesn't have a function for pulling this information directly.
So something like this should work:
lookup.csv
number, ascii
13, "carriage return"
sourcetype=mydata | rex "SQL: CHAR(?<char>\d)" | fields char | lookup chart AS number OUTPUT ascii AS "character"
This will take the numeric values you see and translate them to the ascii values you are looking for.
You will have to create the lookup table, but that is just a csv that follows the pattern that laid out.
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