SQL Dynamic Charindex - sql-server

Question

I have a field in a sql table but I need to parse it via charindex, but the lttle caveat is, I don't know how many pieces there are.
The field data would look like the following:
(Image: "filename=a.jpg"), (Image: "filename=b.jpg")
But the question I'm not sure how many filenames there will be in this string, so i need to dynamically build this out this could be 1 or this could be 100.
Any suggestions?
Thanks

Answer 1

Since you cannot know in advance how many values you will extract from each value, I would suggest to represent the results as records, not columns.
If you are using SQL Server 2016 or higher, you can use function STRING_SPLIT() to turn CSV parts to records. Then, SUBSTRING() and CHARINDEX() can be used to extract the relevant information:
declare #t table ([txt] varchar(200))
insert into #t VALUES ('(Image: "filename=a.jpg"),(Image: "filename=b.jpg")')
SELECT value, SUBSTRING(
value,
CHARINDEX('=', value) + 1,
LEN(value) - CHARINDEX('=', value) - 2
)
FROM #t t
CROSS APPLY STRING_SPLIT(t.txt , ',')
Demo on DB Fiddle:
DECLARE #t table ([txt] varchar(200))
INSERT INTO #t VALUES ('(Image: "filename=a.jpg"),(Image: "filename=b.jpg")')
SELECT value, SUBSTRING(
value,
CHARINDEX('=', value) + 1,
LEN(value) - CHARINDEX('=', value) - 2
)
FROM #t t
CROSS APPLY STRING_SPLIT(t.txt , ',')
GO
value | (No column name)
:------------------------ | :---------------
(Image: "filename=a.jpg") | a.jpg
(Image: "filename=b.jpg") | b.jpg
NB : this assumes that the value to extract is always located after the first equal sign and until 2 characters before the end of string. If the pattern is different, you may need to adapt the SUBSTRING()/CHARINDEX() calls.

Answer 2

The real issue is: This is breaking 1.NF. You should never ever store more than one piece of data in one cell. Such CSV-formats are a pain in the neck and you really should use a related side table to store your image hints one by one.
Nevertheless, this can be handled:
--A mockup table
DECLARE #mockup TABLE(ID INT IDENTITY,YourString VARCHAR(1000));
INSERT INTO #mockup VALUES
('(Image: "filename=a.jpg"), (Image: "filename=b.jpg") ')
,('(Image: "filename=aa.jpg"), (Image: "filename=bb.jpg"), (Image: "filename=cc.jpg"), (Image: "filename=dd.jpg"), (Image: "filename=ee.jpg")');
--Pick one element by its position:
DECLARE #position INT=2;
SELECT CAST('<x>' + REPLACE(t.YourString,',','</x><x>') + '</x>' AS XML)
.value('/x[position()=sql:variable("#position")][1]','nvarchar(max)')
FROM #mockup t;
The trick is, to transform the string to XML and use XQuery to fetch the needed element by its position. The intermediate XML looks like this:
<x>(Image: "filename=a.jpg")</x>
<x> (Image: "filename=b.jpg") </x>
You can use some more replacements and L/RTRIM() to get it cleaner.
Read table data
And if you want to create a clean side table and you need all data neatly separated, you can use a bit more of the same:
SELECT CAST('<x><y><z>'
+ REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(
t.YourString,'(','') --no opening paranthesis
,')','') --no closing paranthesis
,'"','') --no quotes
,' ','') --no blanks
,'=','</z><z>') --Split at "="
,':','</z></y><y><z>') --Split at ":"
,',','</z></y></x><x><y><z>') --Split at ","
+ '</z></y></x>' AS XML)
FROM #mockup t;
This returns
<x>
<y>
<z>Image</z>
</y>
<y>
<z>filename</z>
<z>a.jpg</z>
</y>
</x>
<x>
<y>
<z>Image</z>
</y>
<y>
<z>filename</z>
<z>b.jpg</z>
</y>
</x>
And with this you would get a clean EAV-table (
WITH Casted AS
(
SELECT ID
,CAST('<x><y><z>'
+ REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(
t.YourString,'(','')
,')','')
,'"','')
,' ','')
,'=','</z><z>')
,':','</z></y><y><z>')
,',','</z></y></x><x><y><z>')
+ '</z></y></x>' AS XML) AS CastedToXml
FROM #mockup t
)
SELECT ROW_NUMBER() OVER(ORDER BY (SELECT NULL)) AS ID
,ID AS oldId
,eachElement.value('y[1]/z[1]','varchar(max)') AS DataType
,eachElement.value('y[2]/z[1]','varchar(max)') AS ContentType
,eachElement.value('y[2]/z[2]','varchar(max)') AS Content
FROM Casted
CROSS APPLY CastedToXml.nodes('/x') A(eachElement)
The result
+----+-------+----------+-------------+---------+
| ID | oldId | DataType | ContentType | Content |
+----+-------+----------+-------------+---------+
| 1 | 1 | Image | filename | a.jpg |
+----+-------+----------+-------------+---------+
| 2 | 1 | Image | filename | b.jpg |
+----+-------+----------+-------------+---------+
| 3 | 2 | Image | filename | aa.jpg |
+----+-------+----------+-------------+---------+
| 4 | 2 | Image | filename | bb.jpg |
+----+-------+----------+-------------+---------+
| 5 | 2 | Image | filename | cc.jpg |
+----+-------+----------+-------------+---------+
| 6 | 2 | Image | filename | dd.jpg |
+----+-------+----------+-------------+---------+
| 7 | 2 | Image | filename | ee.jpg |
+----+-------+----------+-------------+---------+

Answer 3

I used a table value function
ALTER FUNCTION [dbo].[Fn_sqllist_to_table](#list AS VARCHAR(8000),
#delim AS VARCHAR(10))
RETURNS #listTable TABLE(
Position INT,
Value VARCHAR(8000))
AS
BEGIN
DECLARE #myPos INT
SET #myPos = 1
WHILE Charindex(#delim, #list) > 0
BEGIN
INSERT INTO #listTable
(Position,Value)
VALUES (#myPos,LEFT(#list, Charindex(#delim, #list) - 1))
SET #myPos = #myPos + 1
IF Charindex(#delim, #list) = Len(#list)
INSERT INTO #listTable
(Position,Value)
VALUES (#myPos,'')
SET #list = RIGHT(#list, Len(#list) - Charindex(#delim, #list))
END
IF Len(#list) > 0
INSERT INTO #listTable
(Position,Value)
VALUES (#myPos,#list)
RETURN
END
By calling it via
select * into #test from tableX as T
cross apply [Fn_sqllist_to_table](fieldname,'(')
and then just substringed the value into the final table