Trouble extracting First and LastName from Full Name column - sql

Question

I am having FullName column and I am extracting the First Name and last name using the following query
select SUBSTRING(FULL_NAME, 1, CHARINDEX(' ', FULL_NAME) - 1) AS FirstName,
SUBSTRING(FULL_NAME, CHARINDEX(' ', FULL_NAME) + 1, 500) AS LastName
from [dbo].[TABLE]
But in the Full Name column there are just First names, some 10 digit phone numbers, 4 digit extensions and some text like 'this is a special case'.
How should I modify my query to accommodate these exceptions? And also when there are only single words in the Full Name column I am getting this following error message:
"Invalid length parameter passed to the LEFT or SUBSTRING function."

Answer 1

Parsing good names from free form fields is not an easy task...
I would suggest a dual approach.
Identify common patterns, i.e. you might find phone number with something like this
Where IsNumeric( Replace(Field,'-','')=1
and you might identify single names with
Where charindex(' ',trim(field))=0
etc.
Once you've identified them, the write code to attempt to split them...
So you might use the code you have above with the following WHERE clause
select SUBSTRING(FULL_NAME, 1, CHARINDEX(' ', FULL_NAME) - 1) AS FirstName,
SUBSTRING(PRQ_BP_CONTACT_NAME, CHARINDEX(' ', FULL_NAME) + 1, 500)
AS LastN
from [dbo].[TABLE]
where charindex(' ',trim(field))>0 and Where IsNumeric( Replace(Field,'-','')=0
Use the WHERE clauses to (a) make sure you only get records you can parse and (b) help identify the oddball cases you'll like need to do by hand...
Good luck

Answer 2

You could go with a function this allows you to put in any logic you need in the transform and keep things a bit more readable :
create function dbo.namepart( #fullname varchar(50), #part varchar(5))
returns varchar(10)
as
begin
declare #first varchar(50)
declare #last varchar(50)
declare #sp int
if #fullname like '%special value%' return ''
if #fullname like '% %'
begin
set #sp = CHARINDEX(' ', #fullname)
set #first = left(#fullname, #sp - 1)
set #last = substring(#fullname,#sp + 1 ,50)
if isnumeric(#last) <> 0 set #last = ''
end
else
begin
set #first = #fullname
set #last = ''
end
if #part like 'f%'
return #first
else
return #last
return ''
end
Sample data
create table blah(
full_name varchar(50)
)
insert into blah values ( 'john smith' ), ('paul 12345'),('evan'),('special value')
And see if it works
select
dbo.namepart(full_name,'first') first,
dbo.namepart(full_name,'last') last,
full_name
from blah
http://sqlfiddle.com/#!6/eb28f/2