SQL Challenge/Puzzle: How to create an ASCII art hierarchy tree with an SQL query?
This was posted on my 1st day on StackOverflow.
It was not really a question, but a knowledge sharing.
Today this question got the "Popular Question Badge".
The initial motivation for this one, was to display Oracles' actual execution plans, saved in GV$SQL_PLAN, in a visual, clear way.
- I've attached my suggested solutions.
- Please feel free to add yours, as long as it fulfills the requirements.
- Please mention the database name your solution was written for.
#Requirements#
Input
- A table containing columns "id" (node's id) and "pid" (node's parent id).
Output
- The result should be a an ASCII art graph (see example below)
- Each pair of "id" and "pid" nodes should be connected with an edge.
- The root node might have an additional single edge.
- There should be no other edged especially not edges that are not connected to any node in one of their sides.
Code
- A single SELECT statement based only on native SQL
- No UDF (User Defined Functions).
- No T-SQL, PL/SQL etc.
##Sample data##
create table h (id int,pid int);
insert into h (id,pid) values (0 ,null);
insert into h (id,pid) values (1 ,0 );
insert into h (id,pid) values (2 ,1 );
insert into h (id,pid) values (3 ,2 );
insert into h (id,pid) values (4 ,3 );
insert into h (id,pid) values (5 ,4 );
insert into h (id,pid) values (6 ,3 );
insert into h (id,pid) values (7 ,6 );
insert into h (id,pid) values (8 ,7 );
insert into h (id,pid) values (9 ,8 );
insert into h (id,pid) values (10 ,9 );
insert into h (id,pid) values (11 ,10 );
insert into h (id,pid) values (12 ,9 );
insert into h (id,pid) values (13 ,12 );
insert into h (id,pid) values (14 ,8 );
insert into h (id,pid) values (15 ,6 );
insert into h (id,pid) values (16 ,15 );
insert into h (id,pid) values (17 ,6 );
insert into h (id,pid) values (18 ,17 );
insert into h (id,pid) values (19 ,17 );
insert into h (id,pid) values (20 ,3 );
insert into h (id,pid) values (21 ,20 );
insert into h (id,pid) values (22 ,21 );
insert into h (id,pid) values (23 ,22 );
insert into h (id,pid) values (24 ,21 );
##Results##
###Vertical siblings###
|
|____ 1
|
|____ 2
|
|____ 3
|
|____ 4
| |
| |____ 5
|
|____ 6
| |
| |____ 7
| | |
| | |____ 8
| | |
| | |____ 9
| | | |
| | | |____ 10
| | | | |
| | | | |____ 11
| | | |
| | | |____ 12
| | | |
| | | |____ 13
| | |
| | |____ 14
| |
| |____ 15
| | |
| | |____ 16
| |
| |____ 17
| |
| |____ 18
| |
| |____ 19
|
|____ 20
|
|____ 21
|
|____ 22
| |
| |____ 23
|
|____ 24
###Horizontal siblings###
|
|
|
0
|
|
|
|
|
1
|
|
|
|
|
2
|
|
|
|
|
3
|
|
---------------------------------------
| | |
| | |
4 6 20
| | |
| | |
| ------------------- |
| | | | |
| | | | |
5 7 15 17 21
| | | |
| | | |
| | ------ ------
| | | | | |
| | | | | |
8 16 18 19 22 24
| |
| |
-------- |
| | |
| | |
9 14 23
|
|
------
| |
| |
10 12
| |
| |
| |
| |
| |
11 13
Solution
SQLite
Vertical siblings
with last_sibling (id)
as
(
select max (id)
from h
group by pid
)
,tree (id,branch,path)
as
(
select 1 as id
,'' as branch
,'001' as path
union all
select h.id
,t.branch || case when ls.id is not null then ' ' else '|' end || ' '
,t.path || '_' || substr ('00000' || h.id,-5)
from tree t
left join last_sibling ls
on ls.id =
t.id
join h
on h.pid =
t.id
)
,vertical_space (n)
as
(
select 1
union all
select vs.n + 1
from vertical_space vs
where vs.n < 2
)
select t.branch || case vs.n when 1 then '|____' || ' ' || cast (t.id as text) else '|' end
from tree t
cross join vertical_space vs
order by t.path
,vs.n desc
;
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