How to repeat (recursive) query, again and again? - sqlite

Question

[EDIT]
Ah.. How can I put "IF" condition when iterate ? sometimes there are no Tags at all.
In that case I do not want any kind of modification.
I wrote query like this;
UPDATE myTable SET myCOL =
substr(myCOL, 1, instr(myCOL, '<Tag>') - 1)
|| '■' ||
substr(myCOL, instr(myCOL, '</Tag>') + 6, length(myCOL));
Because I'd like to achive like this;
myVar := "abc<Tag>BuLah..BuLah..</Tag>def"
myGoal := "abc■def"
So far so good.
Now, things goes to the real world, I have myVar like this;
myVar := "abc<Tag>BuLah1..</Tag>def..ghi<Tag>BuLah2..</Tag>jkl"
How can I achieve my goal ?
Thanks..
[EDIT] Text files attached for the moment.
Link Deleted...
simple extracted text, all ROWs - 811 rows
simple extracted text, all ROWs Tags processed
simple extracted text, Tags ROWs only - 18 rows, 42 tags.
When I execute without this query, its runtime instantly. No time needed. But, when I exectue with this query, it took me 71 seconds to finish. I guess I have made some.. bad bug or something. The other XML parts have handled by the other query, this query deals above mentioned Tags only.

Answer 1

With a recursive CTE:
with recursive cte as (
select myCOL,
substr(myCOL, 1, instr(myCOL, '<Tag>') - 1)
|| '■' ||
substr(myCOL, instr(myCOL, '</Tag>') + 6, length(myCOL)) newCOL
from myTable
where myCOL like '%<Tag>%'
union all
select c.myCOL,
substr(c.newCOL, 1, instr(c.newCOL, '<Tag>') - 1)
|| '■' ||
substr(c.newCOL, instr(c.newCOL, '</Tag>') + 6, length(c.newCOL)) newCOL
from cte c
where c.newCOL like '%<Tag>%'
)
update myTable
set myCOL = (
select newCOL from cte
where myTable.myCOL = cte.myCOL and cte.newCOL not like '%<Tag>%'
)
where myCOL like '%<Tag>%';
See the demo.
Results:
| myCOL |
| ---------------- |
| abc■def |
| abc■def..ghi■jkl |