Splitting out a single field into multiple fields - mysql

Question

I have a table with the following fields:
id, type, date, changelog.
The changelog field has 10 useful pieces of information I would like to split out into their own fields. both new and old: name, month, year, zipcode, status
So I would like to create a table with the following fields:
id, type, date, old_name, new_name, old_month, new_month, old_year, new_year, old_zipcode, new_zipcode, old_status, new_status.
When all 5 pieces of information exist it is easy but when some are missing I can’t get it to work. Any help is appreciated.
a typical changelog field doesn't have all of these pieces of information, just what is being updated.
for example:
id type date changelog
101 upd 1/1/2019 ---!hash:ActiveSupport
name:
- Adam
- Chris
month:
- 7
- 12
status:
- 1
- 3
Which would translate to:
id type date old_name new_name old_month new_month old_year new_year old_zipcode new_zipcode old_status new_status
101 upd 1/1/19 Adam Chris 7 12 1 3

Answer 1

This is not a complete solution (it assumes you can already parse out the values when you know they are present), but it addresses how to handle when those values are missing:
INSERT INTO tableV2 (id, type, date, old_name, new_name, and so on....)
SELECT id, type, date
, CASE WHEN INSTR(changelog, 'name:') = 0 THEN NULL
ELSE (parse the value out here)
END AS old_name
, CASE WHEN INSTR(changelog, 'name:') = 0 THEN NULL
ELSE (parse the value out here)
END AS new_name
, and so on....
FROM tableV1
;
The parsing, while not trivial, probably won't be too difficult other than the tediousness of it. You'll need to take the found "tag" location, find the 3 newlines following it (first for the tag, latter for each value), and then use those along with other string functions such as SUBSTR, LEFT... and maybe some CHAR_LENGTH(tag string) like CHAR_LENGTH('name:') to make the parsing repeatable for each tag with minor modification.