How to extract the n-th value from the text field with delimitors - sql

Question

In SQL table I have a text column with value 'Yellow|Green|Blue' and another column with numeric value. This numeric value defines which part of the text column to be extracted. Values in the text column are separated with '|' separator.
For example:
If numeric value is 0, 1st part of the text field should be extracted: Yellow
If numeric value is 1, 2nd part of the text field should be extracted: Green
And so on.
Is there a way how to extract it dynamically ?
Meaning without using CASE statement like:
case when u.UD_2 =0 then 'Yellow' when u.UD_2=1 then 'Green' when u.UD_2=3 then 'Blue' end Kategorie
UPDATE: We are using SQL Server 2016

Answer 1

This should work for you, in the subquery extract each category to separate columns and after it, use a case statement to choose the needed category.
select case sep when 0 then x.[0] when 1 then x.[1] when 2 then x.[2] end as Kategorie
from (
select *
,LEFT(val, CHARINDEX('|', val) - 1) AS '0'
,LEFT(STUFF(SUBSTRING(val, CHARINDEX('|', val), LEN(val)), 1, 1, ''), CHARINDEX('|', STUFF(SUBSTRING(val, CHARINDEX('|', val), LEN(val)), 1, 1, '')) - 1) AS '1'
,SUBSTRING(SUBSTRING(val, CHARINDEX('|', val), LEN(val)), CHARINDEX('|', val) + 1, LEN(val)) AS '2'
from #test
)x
Sample data:
create table #test
(
val nvarchar(500),
sep int
)
insert into #test values
('Yellow|Green|Blue', 0),
('Yellow|Green|Blue', 1),
('Yellow|Green|Blue', 2)
Note: this only works if there are exact 3 values separated with |
UPDATE
And this is a dynamic way to achieve it, doesn't matter how many categories will be separated:
SELECT x.Kategorie
FROM (
SELECT DISTINCT node.s.value('.', 'NVARCHAR(500)') AS Kategorie
,ROW_NUMBER() OVER (PARTITION BY sep ORDER BY (SELECT NULL)) - 1 as rn
FROM (
SELECT sep
,CAST('<M>' + REPLACE(val, '|', '</M><M>') + '</M>' AS XML) AS Kategorie
FROM #test
) AS s
CROSS APPLY Kategorie.nodes('/M') AS node(s)
)x
JOIN #test AS t ON t.sep = x.rn

Answer 2

One possible approach is to split your text data into substrings and get each substring position.
Starting with SQL Server 2016 you may use STRING_SPLIT() to split a string, but in your case this is not an option, because this function returns a table with all substrings, but they are not ordered and the order of substrings is not guaranteed.
Again, if you use SQL Server 2016+, you may try to transform the text data into a valid JSON array using REPLACE() ('Yellow|Green|Blue' is transformed into '["Yellow","Green","Blue"]') and after that to use OPENJSON() with default schema to retrieve this JSON array as table, which has columns key, value and type (key column contains the index of the element in the specified array).
Input:
CREATE TABLE #Data (
TextValue nvarchar(max),
IndexValue int
)
INSERT INTO #Data
(TextValue, IndexValue)
VALUES
('Yellow|Green|Blue', 0),
('Yellow|Green|Blue', 1)
T-SQL:
SELECT d.TextValue, d.IndexValue, j.[value] AS [Value]
FROM #Data d
CROSS APPLY OPENJSON(CONCAT(N'["', REPLACE(d.TextValue, N'|', N'","'), N'"]')) j
WHERE d.IndexValue = j.[key]
Output:
---------------------------------------
TextValue IndexValue Value
---------------------------------------
Yellow|Green|Blue 0 Yellow
Yellow|Green|Blue 1 Green