SQL Split function that handles string with delimeter appearing between text qualifiers? - sql

Question

There are several SQL split functions, from loop driven, to using xml commands, and even using a numbers table. I haven't found one that supports text qualifiers.
Using the example string below, I would like to split on ",", but not when it appears between double or single quotes.
Example data:
jsmith#anywhere.com, "Sally \"Heat\" Jones" <sally#anywhere.com>, "Mark Jones" <mjones#anywhere.com>, "Stone, Ron" <rstone#anywhere.com>
Should return a table:
jsmith#anywhere.com
"Sally \"Heat\" Jones" <sally#anywhere.com>
"Mark Jones" <mjones#anywhere.com>
"Stone, Ron" <rstone#anywhere.com>
I know this is a complex query/function, but any suggestions or any guidance would be mucho appreciated.

Answer 1

Here is my solution:
CREATE FUNCTION fnSplitString
(
#input nvarchar(MAX)
)
RETURNS #emails TABLE
(
email nvarchar(MAX)
)
AS
BEGIN
DECLARE #len int = LEN(#input)
DECLARE #pos int = 1;
DECLARE #start int = 1;
DECLARE #ignore bit = 0;
WHILE(#pos<=#len)
BEGIN
DECLARE #ch nchar(1) = SUBSTRING(#input, #pos, 1);
IF ( #ch = '"' or #ch = '''')
BEGIN
SET #ignore = 1 - #ignore;
END
IF (#ch = ',' AND #ignore = 0)
BEGIN
INSERT #emails VALUES (SUBSTRING(#input, #start, #pos-#start));
SET #start = #pos+1;
END
SET #pos = #pos + 1;
END
IF (#start<>#pos)
BEGIN
INSERT #emails VALUES (SUBSTRING(#input, #start, #pos-#start));
END
RETURN
END
GO
DECLARE #input nvarchar(max) = 'jsmith#anywhere.com, "Sally \"Heat\" Jones" <sally#anywhere.com>, "Mark Jones" <mjones#anywhere.com>, "Stone, Ron" <rstone#anywhere.com>';
select * from fnSplitString(#input)

Answer 2

CREATE FUNCTION [dbo].[udfSplit]
(
#nvcString nvarchar(max),
#nvcDelimiter nvarchar(1),
#nvcTQ nvarchar(1)
)
RETURNS #tblTokens TABLE (
Token nvarchar(max)
)
AS
BEGIN
DECLARE #intCounter int
DECLARE #nvcToken nvarchar(4000)
DECLARE #nvcCurrentChar nvarchar(1)
DECLARE #intStart int
IF #nvcString <> ''
BEGIN
SET #intCounter = 1
SET #nvcToken = ''
SET #intStart = 0
--Loop through each character of the string
WHILE #intCounter <= LEN(#nvcString)
BEGIN
SET #nvcCurrentChar = SUBSTRING(#nvcString, #intCounter, 1)
--If current char is TQ
IF #nvcCurrentChar = #nvcTQ
BEGIN
--Concatonate to token
SET #nvcToken = #nvcToken + #nvcCurrentChar
--If this is the end TQ
IF #intStart <> 0
BEGIN
--Fix TQ
SET #nvcToken = dbo.udfRemoveTQFromToken(#nvcToken, #nvcTQ)
IF #nvcToken <> ''
BEGIN
INSERT INTO #tblTokens (Token) VALUES (#nvcToken)
SET #nvcToken = ''
END
--Reset TQ
SET #intStart = 0
END
ELSE
BEGIN
SET #nvcToken = dbo.udfRemoveTQFromToken(#nvcToken, #nvcTQ)
IF #nvcToken <> ''
BEGIN
INSERT INTO #tblTokens (Token) VALUES (#nvcToken)
SET #nvcToken = ''
END
--Mark TQ start position
SET #intStart = #intCounter
END
END
ELSE IF #intStart = 0 AND #nvcCurrentChar = #nvcDelimiter
BEGIN
--If not inside TQ, and char is Delimiter
SET #nvcToken = dbo.udfRemoveTQFromToken(#nvcToken, #nvcTQ)
IF #nvcToken <> ''
BEGIN
INSERT INTO #tblTokens (Token) VALUES (#nvcToken)
SET #nvcToken = ''
END
END
ELSE
BEGIN
--Current char is not TQ or Delim, add to current token
SET #nvcToken = #nvcToken + #nvcCurrentChar
END
SET #intCounter = #intCounter + 1
END
END
SET #nvcToken = dbo.udfRemoveTQFromToken(#nvcToken, #nvcTQ)
IF #nvcToken <> ''
BEGIN
--Current Token has not been added to table
INSERT INTO #tblTokens (Token) VALUES (#nvcToken)
END
RETURN
END
GO
CREATE FUNCTION [dbo].[udfRemoveTQFromToken]
(
#nvcToken nvarchar(4000),
#nvcTQ nvarchar(1)
)
RETURNS nvarchar(4000) AS
BEGIN
DECLARE #nvcReturn nvarchar(4000)
--Trim token, needs to be done first,
--as we dont want to trim any spaces within the TQ
--unless it was malformed
SET #nvcReturn = LTRIM(RTRIM(#nvcToken))
--If Left char is TQ
IF LEFT(#nvcReturn, 1) = #nvcTQ
BEGIN
--Though both cases perform the removal of the left most char (opening TQ)
--We need to perform a trim after removal ONLY if it was malformed
IF RIGHT(#nvcReturn, 1) <> #nvcTQ
BEGIN
--But no matching end TQ, malformed
--fix by removing left most char (the opening TQ)
SET #nvcReturn = RIGHT(#nvcReturn, LEN(#nvcReturn) - 1)
--Reapply the LTRIM, incase there were spaces after the opening TQ
SET #nvcReturn = LTRIM(#nvcReturn)
END
ELSE
BEGIN
--has matching end TQ, well-formed
--fix by removing left most char (the opening TQ)
SET #nvcReturn = RIGHT(#nvcReturn, LEN(#nvcReturn) - 1)
END
END
--Remove the right most char (the closing TQ)
IF RIGHT(#nvcReturn, 1) = #nvcTQ
SET #nvcReturn = LEFT(#nvcReturn, LEN(#nvcReturn) - 1)
RETURN #nvcReturn
END

Answer 3

This is a quick solution, and it is less than perfect, it has no stack, so it will treat the comma inside the quotes as the delimiter.
alter function fnSplit
(
#Delim char(1),
#List nvarchar(4000)
)
returns table as
return
with
Strings(PosIdx) as
(
select 1
union all
select PosIdx + 1 from Strings where PosIdx < 4000
)
select
ltrim(rtrim(substring(#List, PosIdx, charindex(#Delim, #List + #Delim, PosIdx) - PosIdx))) as value
from
Strings
where
PosIdx <= convert(int, len(#List))
and substring(#Delim + #List, PosIdx, 1) = #Delim
go
select * from fnSplit(',', 'jsmith#anywhere.com, "Sally \"Heat\" Jones" <sally#anywhere.com>, "Mark Jones" <mjones#anywhere.com>, "Stone, Ron" <rstone#anywhere.com>')
option (maxrecursion 0)