So this can easily be done in SQL.

But since this is string parsing it will be intense on the sql server. So i recommend to rather change the way the data are received.

But if you want to attempt in doing this in sql

here you go:

declare @String varchar(50) = 'CHILD=1625=0n=1==3&ADULT=1900=1j=1==1'

/*

-- Get the text left of the first =

select left(@String,charindex('=',@String,1)-1)

--get the first index of the &

select charindex('&',@String)

-- get the first index of the first = after the first &

select charindex('=',@String,charindex('&',@String))

-- Get the text between the first & and only look at the amount of char to return.

-- First & index + 1The amount of char to return

select SUBSTRING(@String,charindex('&',@String)+1, charindex('=',@String,charindex('&',@String))-charindex('&',@String)-1)

*/

select left(@String,charindex('=',@String,1)-1)+', '+ SUBSTRING(@String,charindex('&',@String)+1,charindex('=',@String,charindex('&',@String))-charindex('&',@String)-1)

I have added some small select statements so you can see what each step is trying to do.

Hope this helps