Remove lines recursively from a SQL TEXT column - sql-server

Question

I have a SQL Text column which has a block of text and has multiple lines which are not relevant and I need to remove only those lines.
Example - This is all one column value:
Header_ID askdjfhklasjdhfklajhfwoi fhweiohrognfk
ABC
SECTION_ID asdfhkwjehfi efjhewiu1382204 3904834
123
SECTION_ID deihefgjkahf dfjsdhfkl edfashldfkljh
So basically I need to remove all lines which are starting with Header_ID and Section_ID and the output Text i need is just
ABC
123
The only thing constant about these lines is the first word it starts with and depending on that I need to remove the whole line.

Answer 1

Here is a solution. Details about how it works are below. Note this solution needs MSSQL 2017+ to work.
-- Place the raw string value as varchar data in a variable so it is convenient to work with:
declare #rawValue varchar(max) = 'Header_ID askdjfhklasjdhfklajhfwoi fhweiohrognfk
ABC
SECTION_ID asdfhkwjehfi efjhewiu1382204 3904834
123
SECTION_ID deihefgjkahf dfjsdhfkl edfashldfkljh';
-- Perform multiple operations on the raw value and save the result to another variable:
declare #convertedValue varchar(max) =
(
select string_agg(value, char(13) + char(10))
from string_split(#rawValue, char(10))
where value not like 'header_id%' and value not like 'section_id%'
);
-- Display converted value.
select #convertedValue;
The magic begins with the string_split() function which produces a table value. It detects the line feed character, char(10), and splits the multi-line string into a table with each line from the string in a separate row.
Next, we filter out the rows from the table that we don't want. These rows begin with the known substrings header_id and section_id. This is accomplished in the where clause.
Lastly, for the output, we use string_agg() and aggregate the remaining rows (the lines we do want) back into a string with the individual values delimited by a combination of the carriage return char(13) and line feed char(10) characters.

Answer 2

Since I am using SQL Server 2016 and not 2017 what i did to resolve the issue was First break all the data into multiple rows(Cross apply with the Split function) using the delimiter as CHAR(13) and then taking only rows that did not start with Header_ID, Section_ID etc and using stuff again built the text block.
Thanks again #otto for the resolution.