-- Databricks notebook source
-- =============================================================================
-- Purpose    : Build the flattened IMS ATC level 1-4 hierarchy.
-- Source     : dwd.dwd_ims_td_therapeutic_class
-- Target     : dwd.dwd_ims_atc_hierarchy
-- Grain      : One row per hierarchy path rooted at ATC1_CODE; lower levels may be null.
-- Write mode : Full refresh (INSERT OVERWRITE).
-- Downstream : dwd.dwd_ims_td_pack_property, dws.dws_ims_td_atc_cn
-- Notes      : Parent-code matching is preserved from the legacy script.
-- =============================================================================

INSERT OVERWRITE TABLE dwd.dwd_ims_atc_hierarchy (
    ATC1_ID,
    ATC1_CODE,
    ATC1_DES,
    ATC2_ID,
    ATC2_CODE,
    ATC2_DES,
    ATC3_ID,
    ATC3_CODE,
    ATC3_DES,
    ATC4_ID,
    ATC4_CODE,
    ATC4_DES
)
WITH therapeutic_class AS (
    SELECT
        therapeutic_id,
        therapeutic_code,
        therapeutic_name,
        therapeutic_level
    FROM dwd.dwd_ims_td_therapeutic_class
),
atc_level_1 AS (
    SELECT
        therapeutic_id AS atc1_id,
        therapeutic_code AS atc1_code,
        therapeutic_name AS atc1_des
    FROM therapeutic_class
    WHERE therapeutic_level = '1'
),
atc_level_2 AS (
    SELECT
        therapeutic_id AS atc2_id,
        therapeutic_code AS atc2_code,
        therapeutic_name AS atc2_des
    FROM therapeutic_class
    WHERE therapeutic_level = '2'
),
atc_level_3 AS (
    SELECT
        therapeutic_id AS atc3_id,
        therapeutic_code AS atc3_code,
        therapeutic_name AS atc3_des
    FROM therapeutic_class
    WHERE therapeutic_level = '3'
),
atc_level_4 AS (
    SELECT
        therapeutic_id AS atc4_id,
        therapeutic_code AS atc4_code,
        therapeutic_name AS atc4_des
    FROM therapeutic_class
    WHERE therapeutic_level = '4'
)
SELECT
    atc_level_1.atc1_id,
    atc_level_1.atc1_code,
    atc_level_1.atc1_des,
    atc_level_2.atc2_id,
    atc_level_2.atc2_code,
    atc_level_2.atc2_des,
    atc_level_3.atc3_id,
    atc_level_3.atc3_code,
    atc_level_3.atc3_des,
    atc_level_4.atc4_id,
    atc_level_4.atc4_code,
    atc_level_4.atc4_des
FROM atc_level_1
LEFT JOIN atc_level_2
    ON atc_level_1.atc1_code = LEFT(atc_level_2.atc2_code, 1)
LEFT JOIN atc_level_3
    ON atc_level_2.atc2_code = LEFT(atc_level_3.atc3_code, 3)
LEFT JOIN atc_level_4
    ON atc_level_3.atc3_code = LEFT(atc_level_4.atc4_code, 4)
;