Pivoting a string from a table function in different columns - sql

Question

I have a task to create a table function that receives a string and sorts it into different columns.
The string itself may vary, but the columns are supposed to be the same always.
The string is: '100^TEst¬200^TEst2¬300^Test3', but for example if I add "¬400^Test4" that should be in the result set as well.
Here is what I've managed to do so far.
if object_id('stringSplit1') is not null
drop function stringSplit1
go
create function stringSplit1(#input varchar(1000))
returns #outputtable table (ord varchar(1000), dta_1 varchar(1000), dta_2 varchar(1000))
as
begin
return
end
go
select [1] as dta_1, [2] as dta_2 from (
select row_number() over(partition by id order by (select null)) as rn, value
from (select value as id from string_split('100^TEst¬200^TEst2¬300^Test3', '¬')) as bo
cross apply string_split(id, '^') as bk) t
pivot(
max([value]) for [rn] in ([1], [2])
) as pvt

Answer 1

Sometimes, in similar cases, a JSON-based approach is also an option. You need to transform the input text into a valid JSON structure ('100^TEst¬200^TEst2¬300^Test3' into [{"100":"TEst"},{"200":"TEst2"},{"300":"Test3"}] ) and parse it with OPENJSON(). The result from this call is a table with columns [Key], [Value] and [Type]. When the parsed text is a JSON array, the [Key] column holds the index of each element in the JSON array.
UDF:
CREATE FUNCTION dbo.StringSplit1 (#Text varchar(8000))
RETURNS table AS
RETURN
SELECT
(CONVERT(int, j1.[key]) + 1) AS [Ord],
j2.[key] AS dat_1,
j2.[value] AS dat_2
FROM OPENJSON(CONCAT('[{"', REPLACE(REPLACE(#Text, '¬', '"},{"'), '^', '":"'), '"}]')) j1
OUTER APPLY OPENJSON(j1.[value]) j2
Statement:
SELECT *
FROM dbo.StringSplit1('100^TEst¬200^TEst2¬300^Test3')
Result:
Ord dat_1 dat_2
---------------
1 100 TEst
2 200 TEst2
3 300 Test3
As an additional note, if you use SQL Server 2017+, you may use STRING_ESCAPE() to escape the input text:
...
FROM OPENJSON(CONCAT(
'[{"',
REPLACE(REPLACE(STRING_ESCAPE(#Text, 'json'), '¬', '"},{"'), '^', '":"'),
'"}]'
)) j1
...

Answer 2

Firstly, although you can use STRING_SPLIT the order of the value returned by it is not guaranteed. As you define the length of your parameter as 1000 in your function stringSplit1 this means we can safely use a function like DelimitedSplit8K_LEAD which does guarantee the order by providing the ordinal position of each value. This means we can do something like this:
SELECT SSr.ItemNumber AS Ord,
MAX(CASE SSc.ItemNumber WHEN 1 THEN SSc.Item END) AS dta_1,
MAX(CASE SSc.ItemNumber WHEN 2 THEN SSc.Item END) AS dta_2
FROM (VALUES('100^TEst¬200^TEst2¬300^Test3'))V(YourColumn)
CROSS APPLY dbo.DelimitedSplit8K_LEAD(V.YourColumn,'¬') SSr
CROSS APPLY dbo.DelimitedSplit8K_LEAD(SSr.Item,'^') SSc
GROUP BY SSr.ItemNumber;
If you want this as a functionm, use an inline table value function, not a multi-line TVF like you have done:
CREATE FUNCTION dbo.DatasetSplit (#Input varchar(8000))
RETURNS table AS
RETURN
SELECT SSr.ItemNumber AS Ord,
MAX(CASE SSc.ItemNumber WHEN 1 THEN SSc.Item END) AS dta_1,
MAX(CASE SSc.ItemNumber WHEN 2 THEN SSc.Item END) AS dta_2
FROM (VALUES(#Input))V(YourColumn)
CROSS APPLY dbo.DelimitedSplit8K_LEAD(V.YourColumn,'¬') SSr
CROSS APPLY dbo.DelimitedSplit8K_LEAD(SSr.Item,'^') SSc
GROUP BY SSr.ItemNumber;
GO
SELECT *
FROM dbo.DatasetSplit ('100^TEst¬200^TEst2¬300^Test3') DS;
If you want to parametrise your row and column delimiters, then you could do it like this:
ALTER FUNCTION dbo.DatasetSplit (#Input varchar(8000), #RowDelimiter char(1), #ColumnDelimiter char(1))
RETURNS table AS
RETURN
SELECT SSr.ItemNumber AS Ord,
MAX(CASE SSc.ItemNumber WHEN 1 THEN SSc.Item END) AS dta_1,
MAX(CASE SSc.ItemNumber WHEN 2 THEN SSc.Item END) AS dta_2
FROM (VALUES(#Input))V(YourColumn)
CROSS APPLY dbo.DelimitedSplit8K_LEAD(V.YourColumn,#RowDelimiter) SSr
CROSS APPLY dbo.DelimitedSplit8K_LEAD(SSr.Item,#ColumnDelimiter) SSc
GROUP BY SSr.ItemNumber;
GO
SELECT *
FROM dbo.DatasetSplit ('100^TEst¬200^TEst2¬300^Test3','¬','^') DS;
Definition of DelimitedSplit8K_LEAD for completeness:
CREATE FUNCTION [dbo].[DelimitedSplit8K_LEAD]
--===== Define I/O parameters
(#pString VARCHAR(8000), #pDelimiter CHAR(1))
RETURNS TABLE WITH SCHEMABINDING AS
RETURN
--===== "Inline" CTE Driven "Tally Table” produces values from 0 up to 10,000...
-- enough to cover VARCHAR(8000)
WITH E1(N) AS (
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1
), --10E+1 or 10 rows
E2(N) AS (SELECT 1 FROM E1 a, E1 b), --10E+2 or 100 rows
E4(N) AS (SELECT 1 FROM E2 a, E2 b), --10E+4 or 10,000 rows max
cteTally(N) AS (--==== This provides the "zero base" and limits the number of rows right up front
-- for both a performance gain and prevention of accidental "overruns"
SELECT 0 UNION ALL
SELECT TOP (DATALENGTH(ISNULL(#pString,1))) ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM E4
),
cteStart(N1) AS (--==== This returns N+1 (starting position of each "element" just once for each delimiter)
SELECT t.N+1
FROM cteTally t
WHERE (SUBSTRING(#pString,t.N,1) = #pDelimiter OR t.N = 0)
)
--===== Do the actual split. The ISNULL/NULLIF combo handles the length for the final element when no delimiter is found.
SELECT ItemNumber = ROW_NUMBER() OVER(ORDER BY s.N1),
Item = SUBSTRING(#pString,s.N1,ISNULL(NULLIF((LEAD(s.N1,1,1) OVER (ORDER BY s.N1) - 1),0)-s.N1,8000))
FROM cteStart s;
GO