Parsing through free text field in SQL - sql

Question

I have a field in my table that has different types of data in it which can be translated into different columns or rows.
Free Text Field
TypeID
{Visit Info}[<Visit Date>2022-01-01</Visit Date><Visit Type>Clinical</Visit Type>]{/Visit Info}{Costs}[<Laboratory>30.91</Laboratory><Encounter>15.00</Encounter>]{/Costs}
1
{Index Events}[<Date>2022-03-04</Date><Diagnosis>I10</Diagnosis>]{/Index Events}
2
{Visit Info}[<Visit Date>2022-10-12</Visit Date><Visit Type>Administrative</Visit Type>]{/Visit Info}{Costs}[<Consultation>25.00</Consultation>]{/Costs}
1
The idea is that the data is enclosed in {Category}, <Subcategory> and then the data related to the <Subcategory>. I need to write a query that returns the data like in the following result set:
TypeID
Category
Subcategory
Result
1
Visit Info
Visit Date
2022-01-01
1
Visit Info
Visit Type
Clinical
1
Costs
Laboratory
30.91
1
Costs
Encounter
15.00
2
Index Events
Date
2022-03-04
2
Index Events
Diagnosis
I10
1
Visit Info
Visit Date
2022-10-12
1
Visit Info
Visit Type
Administrative
1
Costs
Consultation
25.00
I'd appreciate it if I could be pointed to the right direction in terms of what functions to use.
I'm using SSMS on SQL Server 2016
For anyone wondering, I ended up replacing the "{" and "}" values with "<" and ">" respectively and removing the "[" and "]" values.
After this I cast the field as XML and used XML nodes to parse through the field, like so:
SELECT
TypeID,
UniqueID,
[Free Text Field],
tbl.col.value('local-name(..)','VARCHAR(MAX)') AS Name,
tbl.col.value('local-name(.)','VARCHAR(MAX)') AS Name,
tbl.col.value('.[1]','VARCHAR(MAX)') AS Value
FROM [My Table] a
CROSS APPLY [My Table].[Free Text Field].nodes('/*/*') AS tbl(col)

Answer 1

If your data looked like this then it would be valid XML and would be easy to parse with the XML parser
Free Text Field
TypeID
<Visit Info><Visit Date>2022-01-01</Visit Date><Visit Type>Clinical</Visit Type></Visit Info><Costs><Laboratory>30.91</Laboratory><Encounter>15.00</Encounter></Costs>
1
<Index Events><Date>2022-03-04</Date><Diagnosis>I10</Diagnosis></Index Events>
2
<Visit Info><Visit Date>2022-10-12</Visit Date><Visit Type>Administrative</Visit Type></Visit Info><Costs><Consultation>25.00</Consultation></Costs>
1

Answer 2

You can do a lot with substring, like:
WITH cte AS (
SELECt 'Visit Info' as category, 'Visit Date' as subcategory UNION
SELECt 'Costs' as category, 'Laboratory' as subcategory
)
SELECT
typeid,
category,
subcategory,
SUBSTRING(ss,y1+len(subcategory)+2,y2-(y1+len(subcategory)+2)) as value
FROM (
SELECT
typeid,
category,
subcategory,
SUBSTRING(free,x1+len(category)+2,x2-(x1+len(category)+2)) as ss,
CHARINDEX(CONCAT('<',subcategory,'>'),SUBSTRING(free,x1+(len(category)+2),x2-x1+len(category)+2+1)) as y1,
CHARINDEX(CONCAT('</',subcategory,'>'),SUBSTRING(free,x1+(len(category)+2),x2-x1+len(category)+2+1)) as y2
FROM (
SELECT
typeid,
category,
free,
subcategory,
CHARINDEX(CONCAT('{',category,'}'),free) as x1,
CHARINDEX(CONCAT('{/',category,'}'),free) as x2
FROM test
CROSS APPLY cte )x
WHERE x1<>0 and x2>x1
) y
WHERE y1<>0 and y2>y1 ;
The other category and subcategory's can be done in the same way
Output of this:
typeid
category
subcategory
value
1
Costs
Laboratory
30.91
1
Visit Info
Visit Date
2022-01-01
1
Visit Info
Visit Date
2022-10-12
see: DBFIDDLE