Query WHERE Only Alphabetic Characters - sql

Question

I am trying to filter out data in my Excel sheet of customers for my company.
The three fields I need to by are FIRST_NAME, LAST_NAME, and COMPANY_NAME.
The rules are as follows:
FIRST_NAME AND LAST_NAME must NOT be NULL
FIRST_NAME AND LAST_NAME must be only alphabetic
The above rules are irrelevant IF COMPANY_NAME is NOT NULL
So, just to reiterate to be clear.. A customer must have a FIRST_NAME AND a LAST_NAME (They cannot be missing one or both), BUT, if they have a COMPANY_NAME they are allowed to not have a FIRST_NAME and/or LAST_NAME.
Here's some example data and if they should stay in the data or not:
FIRST_NAME | LAST_NAME | COMPANY_NAME | Good customer?
-----------|-----------|--------------|--------------------------------
Alex | Goodman | AG Inc. | Yes - All are filled out
John | Awesome | | Yes - First and last are fine
Cindy | | Cindy Corp. | Yes - Company is filled out
| | Blank Spa | Yes - Company is filled out
| | | No - Nothing is filled out
Gordon | Mang#2 | | No - Last contains non-alphabet
Jesse#5 | Levvitt | JL Inc. | Yes - Company is filled out
Holly | | | No - No last or company names
Here is the query (With some fields in the SELECT clause removed):
SELECT VR_CUSTOMERS.CUSTOMER_ID, VR_CUSTOMERS.FIRST_NAME, VR_CUSTOMERS.LAST_NAME, VR_CUSTOMERS.COMPANY_NAME, ...
FROM DEV.VR_CUSTOMERS VR_CUSTOMERS
WHERE (
LENGTH(NAME)>4 AND
(UPPER(NAME) NOT LIKE UPPER('%delete%')) AND
(COMPANY_NAME IS NOT NULL OR (COMPANY_NAME IS NULL AND FIRST_NAME IS NOT NULL AND LAST_NAME IS NOT NULL AND FIRST_NAME LIKE '%^[A-z]+$%' AND LAST_NAME LIKE '%^[A-z]+$%'))
)
I've tried as well the regex of '%[^a-z]%'. I've tried RLIKE and REGEXP, instead of LIKE, and those did not seem to work either.
With the above query, the results only show records with a COMPANY_NAME.

Answer 1

Fixed the issue using REGEXP_LIKE and the regex ^[A-z]+$.
Here is the WHERE clause after this fix:
WHERE (
LENGTH(NAME)>4 AND
(UPPER(NAME) NOT LIKE UPPER('%delete%')) AND
(COMPANY_NAME IS NOT NULL OR (COMPANY_NAME IS NULL AND REGEXP_LIKE(FIRST_NAME, '^[A-z]+$') AND REGEXP_LIKE(LAST_NAME, '^[A-z]+$')))
)

Answer 2

It appears you're using MySQL given your mention of RLIKE and REGEXP. In that case, try this WHERE clause, that uses the regular expression character class 'alpha':
WHERE
COMPANY_NAME is not null -- COMPANY_NAME being present is the higher priority pass condition
or ( -- but if COMPANY_NAME is not present, then the following conditions must be satisfied
FIRST_NAME is not null
and FIRST_NAME REGEXP '[[:alpha:]]+'
and LAST_NAME is not null
and LAST_NAME REGEXP '[[:alpha:]]+'
)
Bear in mind that the not null check is redundant given the regular expression, so the WHERE clause would simplify itself to:
WHERE
COMPANY_NAME is not null -- COMPANY_NAME being present is the higher priority pass condition
or ( -- but if COMPANY_NAME is not present, then the following conditions must be satisfied
FIRST_NAME REGEXP '[[:alpha:]]+'
and LAST_NAME REGEXP '[[:alpha:]]+'
)