Edit string column in SQL - remove sections between separators - sql

Question

I have a string column in my table that contains 'Character-separated' data such as this:
"Value|Data|4|Z|11/06/2012"
This data is fed into a 'parser' and deserialised into a particular object. (The details of this aren't relevant and can't be changed)
The structure of my object has changed and now I would like to get rid of some of the 'sections' of data
So I want the previous value to turn into this
"Value|Data|11/06/2012"
I was hoping I might be able to get some help on how I would go about doing this in T-SQL.
The data always has the same number of sections, 'n' and I will want to remove the same sections for all rows , 'n-x and 'n-y'
So far I know I need an update statement to update my column value.
I've found various ways of splitting a string but I'm struggling to apply it to my scenario.
In C# I would do
string RemoveSecitons(string value)
{
string[] bits = string.split(value,'|');
List<string> wantedBits = new List<string>();
for(var i = 0; i < bits.Length; i++)
{
if ( i==2 || i==3) // position of sections I no longer want
{
continue;
}
wantedBits.Add(bits[i]);
}
return string.Join(wantedBits,'|');
}
But how I would do this in SQL I'm not sure where to start. Any help here would be appreciated
Thanks
Ps. I need to run this SQL on SQL Server 2012
Edit: It looks like parsing to xml in some manner could be a popular answer here, however I can't guarantee my string won't have characters such as '<' or '&'

Answer 1

Using NGrams8K you can easily write a nasty fast customized splitter. The logic here is based on DelimitedSplit8K. This will likely outperform even the C# code you posted.
DECLARE #string VARCHAR(8000) = '"Value|Data|4|Z|11/06/2012"',
#delim CHAR(1) = '|';
SELECT newString =
(
SELECT SUBSTRING(
#string, split.pos+1,
ISNULL(NULLIF(CHARINDEX(#delim,#string,split.pos+1),0),8000)-split.pos)
FROM
(
SELECT ROW_NUMBER() OVER (ORDER BY d.Pos), d.Pos
FROM
(
SELECT 0 UNION ALL
SELECT ng.position
FROM samd.ngrams8k(#string,1) AS ng
WHERE ng.token = #delim
) AS d(Pos)
) AS split(ItemNumber,Pos)
WHERE split.ItemNumber IN (1,2,5)
ORDER BY split.ItemNumber
FOR XML PATH('')
);
Returns:
newString
----------------------------
"Value|Data|11/06/2012"

Answer 2

Not the most elegant way, but works:
SELECT SUBSTRING(#str,1, CHARINDEX('|',#str,CHARINDEX('|',#str,1)+1)-1)
+ SUBSTRING(#str, CHARINDEX('|',#str,CHARINDEX('|',#str,CHARINDEX('|',#str,CHARINDEX('|',#str,1)+1)+1)+1), LEN(#str))
----------------------
Value|Data|11/06/2012

Answer 3

You might try some XQuery:
DECLARE #s VARCHAR(100)='Value|Data|4|Z|11/06/2012';
SELECT CAST('<x>' + REPLACE(#s,'|','</x><x>') + '</x>' AS XML)
.value('concat(/x[1],"|",/x[2],"|",/x[5])','nvarchar(max)');
In short: The value is trasformed to XML by some string replacements. Then we use the XQuery-concat to bind the first, the second and the fifth element together again.
This version is a bit less efficient but safe with forbidden characters:
SELECT CAST('<x>' + REPLACE((SELECT #s AS [*] FOR XML PATH('')),'|','</x><x>') + '</x>' AS XML)
.value('concat(/x[1],"|",/x[2],"|",/x[5])','nvarchar(max)')

Answer 4

Just to add a non-xml option for fun:
Edit and Caveat - In case anyone tries this for a different solution and doesn't read the comments...
HABO rightly noted that this is easily broken if any of the columns have a period (".") in them. PARSENAME is dependent on a 4 part naming structure and will return NULL if that is exceeded. This solution will also break if any values ever contain another pipe ("|") or another delimited column is added - the substring in my answer is specifically there as a workaround for the dependency on the 4 part naming. If you are trying to use this solution on, say, a variable with 7 delimited columns, it would need to be reworked or scrapped in favor of one of the other answers here.
DECLARE
#a VARCHAR(100)= 'Value|Data|4|Z|11/06/2012'
SELECT
PARSENAME(REPLACE(SUBSTRING(#a,0,LEN(#a)-CHARINDEX('|',REVERSE(#a))+1),'|','.'),4)+'|'+
PARSENAME(REPLACE(SUBSTRING(#a,0,LEN(#a)-CHARINDEX('|',REVERSE(#a))+1),'|','.'),3)+'|'+
SUBSTRING(#a,LEN(#a)-CHARINDEX('|',REVERSE(#a))+2,LEN(#a))

Answer 5

Here is a quick way to do it.
CREATE FUNCTION [dbo].StringSplitXML
(
#String VARCHAR(MAX), #Separator CHAR(1)
)
RETURNS #RESULT TABLE(id int identity(1,1),Value VARCHAR(MAX))
AS
BEGIN
DECLARE #XML XML
SET #XML = CAST(
('<i>' + REPLACE(#String, #Separator, '</i><i>') + '</i>')
AS XML)
INSERT INTO #RESULT
SELECT t.i.value('.', 'VARCHAR(MAX)')
FROM #XML.nodes('i') AS t(i)
WHERE t.i.value('.', 'VARCHAR(MAX)') <> ''
RETURN
END
GO
SELECT * FROM dbo.StringSplitXML( 'Value|Data|4|Z|11/06/2012','|')
WHERE id not in (3,4)
Note that using a UDF will slow things down, so this solution should be considered only if you have a reasonably small data set to work with.