Converting SQL statement to Regular Expression - can it be done? - sql

Question

I need to convert the below SQL statement into Regular Expression.
CASE WHEN TypeCode >= 400
AND TypeCode < 700
THEN Amt * -1
ELSE Amt
END
Background: I am putting a bank transactions file (BAI2 file) in to a system for transactional matching (matching bank transactions to GL transactions). In order to get these transactions to match, the fields to match on have to be exactly the same. However, in the GL a $500 check may be input as -500 (because the company's cash account is being reduced by $500 for a utility bill), but BAI files store all amounts as positive values. I need to use the transaction type code from the bank to identify whether an amount should be a debit or a credit (in reference to the GL).
I have SQL developers that can do this using SQL, but this tool I'm using to do the BAI data manipulation requires the logic to be input as Regular Expression.
Can anyone assist in applying the appropriate signage (positive or negative) to these amounts for bank transactions? Can this even be done? I'm a new poster so please bear with any ignorance and let me know if I can provide further details/information.

Answer 1

Maybe try this:
^[4-6][0-9]{2}$
This will look for numbers between 400-699 inclusive.
EDIT: Changed \d to [0-9] as \d may include weird characters as well.

Answer 2

I feel your pain...no bank makes it easy.
'\d' means exactly '[0-9]', '\d' is shorter.
Banks have done a good job at fooling the masses that the word 'credit' is good and 'debit' is bad (me thinks that is their intent...).
You can't know if the value should be negative or positive unless you KNOW which direction the money is flowing in.
IF the table has separate columns for INWARDS/RECEIVED funds and OUTWARDS/PAID funds, then you do not need positive and negative indication.
IF, however, there is only ONE column in the table for all AMOUNTS, whether moved INTO or taken OUT FROM the account, then you definitely need SIGNED VALUES (positive/negative indication).
Either "-$nnn" or "($nnn)", with or without the "$".
If you have TWO COLUMN tables (PAID IN and PAID OUT) then just use "$nnn" without SIGNS.
If you have a SINGLE COLUMN table, then you can replace "$" with "-$" using:
$value =~ s/\$/-\$/;
The above is a perl example.
'\$' means "literal SIGIL" (i.e. dollar sign).
To match any value between and including 399-700 use the following regex:
^(399|[4-6]\d\d|700)$
That should match exactly what you want.
So you could do something like (in perl):
if ($TypeCode =~ m/^([4-6]\d\d|399|700)$/) { # if code matches pattern
# -EITHER-
$Amount=~ s/\$/-\$/; # prepend "-" to "$"
# -OR-
$Amount=~ s/\$/-/; # replace "$" with "-"
}
The '^' (carat - start of line or string) and '$' (sigil - end of line or string) surrounding the regex stop it from matching anything with 4 or more digits, like 3399 or 47421.
I moved '[4-6]\d\d' to the front as that will match 300 of 302 possible codes (and, I dunno, it may save a few milliseconds of processing).
'[4-6]' = '[456]', which means the digits from '4' to '6'.
TEST THIS ON SAMPLE DATA FIRST!