pl sql query recuresive looping - postgresql

Question

i have only one table "tbl_test"
Which have table filed given below
tbl_test table
trx_id | proj_num | parent_num|
1 | 14 | 0 |
2 | 14 | 1 |
3 | 14 | 2 |
4 | 14 | 0 |
5 | 14 | 3 |
6 | 15 | 0 |
Result i want is : when trx_id value 5 is fetched
it's a parent child relationship. so,
trx_id -> parent_num
5 -> 3
3 -> 2
2 -> 1
That means output value:
3
2
1
Getting all parent chain
Query i used :
SELECT * FROM (
WITH RECURSIVE tree_data(project_num, task_num, parent_task_num) AS(
SELECT project_num, task_num, parent_task_num
FROM tb_task
WHERE project_num = 14 and task_num = 5
UNION ALL
SELECT child.project_num, child.task_num, child.parent_task_num
FROM tree_data parent Join tb_task child
ON parent.task_num = child.task_num AND parent.task_num = child.parent_task_num
)
SELECT project_num, task_num, parent_task_num
FROM tree_data
) AS tree_list ;
Can anybody help me ?

Answer 1

There's no need to do this with pl/pgsql. You can do it straight in SQL. Consider:
WITH RECURSIVE my_tree AS (
SELECT trx_id as id, parent_id as parent, trx_id::text as path, 1 as level
FROM tbl_test
WHERE trx_id = 5 -- start value
UNION ALL
SELECT t.trx_id, t.parent_id, p.path || ',' || t.trx_id::text, p.level + 1
FROM my_tree p
JOIN tbl_text t ON t.trx_id = p.parent
)
select * from my_tree;

Answer 2

If you are using PostgresSQL, try using a WITH clause:
WITH regional_sales AS (
SELECT region, SUM(amount) AS total_sales
FROM orders
GROUP BY region
), top_regions AS (
SELECT region
FROM regional_sales
WHERE total_sales > (SELECT SUM(total_sales)/10 FROM regional_sales)
)
SELECT region,
product,
SUM(quantity) AS product_units,
SUM(amount) AS product_sales
FROM orders
WHERE region IN (SELECT region FROM top_regions)
GROUP BY region, product;