Create multiple categories with parent, child and grandchild - mysql

Question

I want to create multiple categories with parent, child and grandchild.
And can order by ordering field.
id | parent_id | name | ordering
--------------------------------------
1 | 0 | Men | 1
2 | 0 | Women | 2
3 | 1 | Shoes | 3
4 | 2 | Watches | 4
5 | 1 | Pants | 5
6 | 3 | Sport | 6
7 | 3 | Casual | 7
8 | 2 | Book | 8
I want this result
Men
Shoes
Sport
Casual
Pants
Women
Watches
Book
Array out put
Array
(
[0] => Array
(
[id] => 1
[parent_id] => 0
[name] => Men
[ordering] => 1
[level] => parent //NEEDED
)
[1] => Array
(
[id] => 2
[parent_id] => 0
[name] => Women
[ordering] => 2
[level] => parent //NEEDED
)
[2] => Array
(
[id] => 3
[parent_id] => 1
[name] => Shoes
[ordering] => 3
[level] => child //NEEDED
)
[3] => Array
(
[id] => 4
[parent_id] => 2
[name] => Watches
[ordering] => 4
[level] => child //NEEDED
)
[4] => Array
(
[id] => 5
[parent_id] => 1
[name] => Pants
[ordering] => 5
[level] => child //NEEDED
)
[5] => Array
(
[id] => 6
[parent_id] => 3
[name] => Sport
[ordering] => 6
[level] => grandchild //NEEDED
)
[6] => Array
(
[id] => 7
[parent_id] => 3
[name] => Casual
[ordering] => 7
[level] => grandchild //NEEDED
)
[7] => Array
(
[id] => 8
[parent_id] => 2
[name] => Book
[ordering] => 8
[level] => child //NEEDED
)
)

Answer 1

This could be a solution to get your level information:
SELECT CASE WHEN parent_id = 0 THEN 'Parent'
ELSE CASE WHEN (SELECT T2.parent_id
FROM tab T2
WHERE T2.id = T.parent_id) = 0 THEN 'Child'
ELSE 'Grandchild'
END
END AS level
FROM tab T
Fiddle here
To put the content of this SQL into an array you need a server side language like PHP, since you're not using mongoDB or similar.

Answer 2

Assuming your table is called "items", you could do the following recursive query to generate names containing the parent and the ordering attribute, then order by the generated name and add spaces before the name according to the level:
;WITH itemsHierarchy (id, parent_id, name, generatedname, level)
AS
(
SELECT
i.id,
i.parent_id,
i.name,
CAST(i.name AS varchar(MAX)) as generatedname,
1 as level
FROM items i
WHERE i.parent_id = 0
UNION ALL
SELECT
i.id,
i.parent_id,
i.name,
CAST(ih.generatedname + '_' + CAST(i.ordering as varchar(2))+ '_' + i.name AS varchar(MAX)),
ih.level + 1
FROM items i
INNER JOIN itemsHierarchy ih ON i.parent_id = ih.id
)
SELECT REPLICATE(' ', level) + name
FROM itemsHierarchy
ORDER BY generatedname
Result:
Men
Shoes
Sport
Casual
Pants
Women
Watches
Book

Answer 3

Finally i found good answer
ref : Parent child mysql
select t0.*,
concat(
case coalesce(t4.parent_id, 0)
when 0 then ''
else concat(cast(t4.parent_id as char), '\\')
end,
case coalesce(t3.parent_id, 0)
when 0 then ''
else concat(cast(t3.parent_id as char), '\\')
end,
case coalesce(t2.parent_id, 0)
when 0 then ''
else concat(cast(t2.parent_id as char), '\\')
end,
case coalesce(t1.parent_id, 0)
when 0 then ''
else concat(cast(t1.parent_id as char), '\\')
end,
case coalesce(t0.parent_id, 0)
when 0 then ''
else concat(cast(t0.parent_id as char), '\\')
end,
cast(t0.id as char)
) as path
from mytable t0
left join mytable t1 on t0.parent_id = t1.Id
left join mytable t2 on t1.parent_id = t2.Id
left join mytable t3 on t2.parent_id = t3.Id
left join mytable t4 on t3.parent_id = t4.Id
order by
concat(
case coalesce(t4.parent_id, 0)
when 0 then ''
else concat(cast(t4.parent_id as char), '\\')
end,
case coalesce(t3.parent_id, 0)
when 0 then ''
else concat(cast(t3.parent_id as char), '\\')
end,
case coalesce(t2.parent_id, 0)
when 0 then ''
else concat(cast(t2.parent_id as char), '\\')
end,
case coalesce(t1.parent_id, 0)
when 0 then ''
else concat(cast(t1.parent_id as char), '\\')
end,
case coalesce(t0.parent_id, 0)
when 0 then ''
else concat(cast(t0.parent_id as char), '\\')
end,
cast(t0.id as char)
)