SQL Server convert xml to csv using CTE - nulls currently being ignored - sql

Question

I am using CTE to convert xml to csv so that it can be exported to a file, however if I have an empty xml tag, this currently gets ignored.
Here is my initial solution courtesy of this previous very helpful post:
https://stackoverflow.com/a/23785202/6260721
Here is my sql:
CREATE TABLE EXPORT_TEST
(
DATA varchar(max)
)
INSERT INTO EXPORT_TEST (DATA)
VALUES ('<EXPORT_DATA><ID>ABC123</ID><PRICE_A>5.6</PRICE_A><PRICE_B></PRICE_B><PRICE_C>8.1</PRICE_C></EXPORT_DATA>')
DECLARE #commaSeparatedValues NVARCHAR(MAX)
DECLARE #xml XML = (SELECT TOP 1 CONVERT(xml,DATA) FROM EXPORT_TEST)
;WITH cte AS (
SELECT
rownr = ROW_NUMBER() OVER (ORDER BY #commaSeparatedValues),
Tbl.col.query('.') AS [xml]
FROM #xml.nodes('EXPORT_DATA') Tbl(col)
), cols AS (
SELECT
rownr,
Tbl.Col.value('.', 'nvarchar(max)') AS Value
FROM cte
CROSS APPLY cte.xml.nodes('//text()') Tbl(Col)
)
INSERT INTO EXPORT_TEST(DATA)
SELECT DISTINCT
STUFF((
SELECT ',' + IIF(ISNUMERIC(value) = 1, Value, '''' + Value + '''')
FROM cols SSF WHERE SSF.rownr = S.rownr
FOR XML PATH(''),TYPE
).value('.','VARCHAR(MAX)'
), 1, 1, '') as DATA
FROM cols S
SELECT * FROM EXPORT_TEST
At the moment, it is returning:
'ABC123',5.6,8.1
But I don't want it to ignore PRICE_B, I want it to return an empty string:
'ABC123',5.6,,8.1 <--extra comma required where PRICE_B should be
How can I achieve this?

Answer 1

Besides the possibility to shredd the full XML and re-concatenate its values (there is an answer already), you might use FLWOR-XQuery:
DECLARE #xml XML=
'<EXPORT_DATA>
<ID>ABC123</ID>
<PRICE_A>5.6</PRICE_A>
<PRICE_B />
<PRICE_C>8.1</PRICE_C>
</EXPORT_DATA>';
EDIT better to read with a variable $txt instead of ($n/text())[1]
SELECT
STUFF
(
#xml.query('
let $r:=/EXPORT_DATA
for $n in $r/*
let $txt:=($n/text())[1]
return if(empty($txt) or not(empty(number($txt)))) then
concat(",",string($txt))
else concat(",''",string($txt),"''")
').value('.','nvarchar(max)'),1,1,'');
The result
'ABC123' ,5.6 , ,8.1

Answer 2

This code works on a mass of records using XQUERY.
I'm assuming char(10) (Line Feed) does not appear in your data.
I'm assuming the maximum length of the concatenated text is 1000 (I don't want to use varchar(max) for no good reason)
You can change both of these assumptions if you wish
declare #separator char(1) = char(10)
select substring
(
replace
(
cast
(
cast(DATA as xml).query
(
'for $i in //*
where not($i/*)
return concat
(
sql:variable("#separator")
,if(local-name($i) = "ID") then ('''''''') else ('''')
,($i/text())[1]
,if(local-name($i) = "ID") then ('''''''') else ('''')
)'
) as nvarchar(1000)
) ,' ' + #separator ,','
) ,2 ,1000
) as csv
from EXPORT_TEST
INSERT INTO EXPORT_TEST (DATA) VALUES
('<EXPORT_DATA><ID>ABC123</ID><PRICE_A>5.6</PRICE_A><PRICE_B></PRICE_B><PRICE_C>8.1</PRICE_C></EXPORT_DATA>')
,('<EXPORT_DATA><ID>DEF456</ID><PRICE_A>6.7</PRICE_A><PRICE_B>66.77</PRICE_B><PRICE_C>7.2</PRICE_C></EXPORT_DATA>')
,('<EXPORT_DATA><ID>GHI789</ID><PRICE_A></PRICE_A><PRICE_B>88.99</PRICE_B><PRICE_C></PRICE_C></EXPORT_DATA>')
csv
'ABC123',5.6,,8.1
'DEF456',6.7,66.77,7.2
'GHI789',,88.99,

Answer 3

What about this:
;WITH cte AS (
SELECT
rownr = ROW_NUMBER() OVER (ORDER BY #commaSeparatedValues),
Tbl.col.query('.') AS [xml]
FROM #xml.nodes('EXPORT_DATA') Tbl(col)
), cols AS (
SELECT
rownr,
Tbl.Col.value('.', 'nvarchar(max)') AS Value
FROM cte
CROSS APPLY cte.xml.nodes('EXPORT_DATA/child::node()') Tbl(Col)
)
INSERT INTO EXPORT_TEST(DATA)
SELECT DISTINCT
STUFF((
SELECT ',' + IIF(ISNUMERIC(value) = 1 OR LEN(value) = 0, Value, '''' + Value + '''')
FROM cols SSF WHERE SSF.rownr = S.rownr
FOR XML PATH(''),TYPE
).value('.','VARCHAR(MAX)'
), 1, 1, '') as DATA
FROM cols S
Using cte.xml.nodes('EXPORT_DATA/child::node()') in the second CTE will give as all nodes:
;WITH cte AS (
SELECT
rownr = ROW_NUMBER() OVER (ORDER BY #commaSeparatedValues),
Tbl.col.query('.') AS [xml]
FROM #xml.nodes('EXPORT_DATA') Tbl(col)
)
SELECT
rownr
,Tbl.Col.query('.')
,Tbl.Col.value('.', 'nvarchar(max)') AS Value
FROM cte
CROSS APPLY cte.xml.nodes('EXPORT_DATA/child::node()') Tbl(Col)
Then, in the concatenation we need to add check for empty string:
IIF(ISNUMERIC(value) = 1 OR LEN(value) = 0, Value, '''' + Value + '''')