Hi Don,
Yes, its better to use it in category table...
Bryan, how many levels there will be - we dont know...
With one table - and ltree is solved all cases...
To add new subcategory user just picks the parent category... So it is easy
to add chain ring to gear... As category...
In another transaction table is category_id, amount...
Don already posted query for sum... In these case just category and
transaction table should be joined sum amount, group by functions on
lpath....(depending what is the goal...)
Kind Regards,
Misa
On Saturday, February 23, 2013, Bryan L Nuse wrote:
>
>>
>> This works fine:
>> test_ltree=> SELECT path, trans_amt FROM testcat;
>> path | trans_amt
>> -----------------------------------------+-----------
>> TOP.Transportation.Auto.Fuel | 50.00
>> TOP.Transportation.Auto.Maintenance | 30.00
>> TOP.Transportation.Auto.Fuel | 25.00
>> TOP.Transportation.Bicycle.Gear | 40.00
>> TOP.Transportation.Bicycle.Gear | 20.00
>> TOP.Transportation.Fares.Bus | 10.00
>> TOP.Transportation.Fares.Train | 5.00
>> TOP.Groceries.Food.Beverages | 30.00
>> TOP.Groceries.Food.Fruit_Veggies | 40.00
>> TOP.Groceries.Food.Meat_Fish | 80.00
>> TOP.Groceries.Food.Grains_Cereals | 30.00
>> TOP.Groceries.Beverages.Alcohol.Beer | 25.00
>> TOP.Groceries.Beverages.Alcohol.Spirits | 10.00
>> TOP.Groceries.Beverages.Alcohol.Wine | 50.00
>> TOP.Groceries.Beverages.Juice | 45.00
>> TOP.Groceries.Beverages.Other | 15.00
>> (16 rows)
>>
>>
>> So if I want to see:
>> TOP.Groceries | 240.00
>> TOP.Transportation | 180.00
>>
>>
>>
> Hello Don,
>
> Perhaps I am missing something about what your constraints are, or what
> you're trying to achieve, but is there any reason you could not use a
> series of joined tables indicating parent-child relationships? The
> following example follows that in your previous posts. Note that this
> approach (as given) will not work if branches stemming from the same node
> are different lengths. That is, if you have costs associated with
> "Transportation.Bicycle.Gear", you could not also have a category
> "Transportation.Bicycle.Gear.Chain_ring". (To add the latter category,
> you'd have to put costs from the former under something like
> "Transportation.Bicycle.Gear.General" -- or modify the approach.) However,
> lengthening the "Alcohol" branches, e.g., by tacking on a level5 table
> would be easy. Notice that level3 and level4 are not true look-up
> tables, since they may contain duplicate cat values.
>
> If I'm off base, by all means specify just how.
>
> Regards,
> Bryan
>
> --------------------------------------------------
>
> CREATE TABLE level1 (
> cat text PRIMARY KEY
> );
>
> CREATE TABLE level2 (
> cat text PRIMARY KEY,
> parent text REFERENCES level1(cat)
> );
>
> CREATE TABLE level3 (
> cat text,
> parent text REFERENCES level2(cat),
> cost numeric(6,2)
> );
>
> CREATE TABLE level4 (
> cat text,
> parent text,
> cost numeric(6,2)
> );
>
>
> INSERT INTO level1
> VALUES ('Transportation'),
> ('Groceries');
>
> INSERT INTO level2
> VALUES ('Auto', 'Transportation'),
> ('Bicycle', 'Transportation'),
> ('Fares', 'Transportation'),
> ('Food', 'Groceries'),
> ('Beverages', 'Groceries');
>
> INSERT INTO level3
> VALUES ('Fuel', 'Auto', 50.00),
> ('Maintenance', 'Auto', 30.00),
> ('Fuel', 'Auto', 25.00),
> ('Gear', 'Bicycle', 40.00),
> ('Gear', 'Bicycle', 20.00),
> ('Bus', 'Fares', 10.00),
> ('Train', 'Fares', 5.00),
> ('Beverages', 'Food', 30.00),
> ('Fruit_Veg', 'Food', 40.00),
> ('Meat_Fish', 'Food', 80.00),
> ('Grains_Cereals', 'Food', 30.00),
> ('Alcohol', 'Beverages', NULL),
> ('Juice', 'Beverages', 45.00),
> ('Other', 'Beverages', 15.00);
>
> INSERT INTO level4
> VALUES ('Beer', 'Alcohol', 25.00),
> ('Spirits', 'Alcohol', 10.00),
> ('Wine', 'Alcohol', 50.00);
>
>
> CREATE VIEW all_cats AS (
> SELECT a.cat AS level4,
> b.cat AS level3,
> c.cat AS level2,
> d.cat AS level1,
> CASE WHEN a.cost IS NULL THEN 0
> WHEN a.cost IS NOT NULL THEN a.cost
> END
> + CASE WHEN b.cost IS NULL THEN 0
> WHEN b.cost IS NOT NULL THEN b.cost
> END AS cost
> FROM level4 a
> FULL JOIN
> level3 b
> ON (a.parent = b.cat)
> FULL JOIN
> level2 c
> ON (b.parent = c.cat)
> FULL JOIN
> level1 d
> ON (c.parent = d.cat)
> ORDER BY level1, level2, level3, level4
> );
>
>
>
> SELECT * FROM all_cats;
>
> level4 | level3 | level2 | level1 | cost
> ---------+----------------+-----------+----------------+-------
> Beer | Alcohol | Beverages | Groceries | 25.00
> Spirits | Alcohol | Beverages | Groceries | 10.00
> Wine | Alcohol | Beverages | Groceries | 50.00
> | Juice | Beverages | Groceries | 45.00
> | Other | Beverages | Groceries | 15.00
> | Beverages | Food | Groceries | 30.00
> | Fruit_Veg | Food | Groceries | 40.00
> | Grains_Cereals | Food | Groceries | 30.00
> | Meat_Fish | Food | Groceries | 80.00
> | Fuel | Auto | Transportation | 50.00
> | Fuel | Auto | Transportation | 25.00
> | Maintenance | Auto | Transportation | 30.00
> | Gear | Bicycle | Transportation | 20.00
> | Gear | Bicycle | Transportation | 40.00
> | Bus | Fares | Transportation | 10.00
> | Train | Fares | Transportation | 5.00
> (16 rows)
>
>
>
>
> SELECT level1,
> count(cost) AS num_branches,
> sum(cost) AS total_cost
> FROM all_cats
> GROUP BY level1
> ORDER BY level1;
>
> level1 | num_branches | total_cost
> ----------------+--------------+------------
> Groceries | 9 | 325.00
> Transportation | 7 | 180.00
> (2 rows)
>
>
