Penggunaan Jinja lanjutan dengan dbt

Studi Kasus: Membangun Model Data E-Commerce dengan dbt

Susan Sun

Freelance Data Scientist

Pernyataan Jinja: loop

Pernyataan Jinja berada dalam {% %}:

Looping item

Templat:
```
{% for ... %} ... {% endfor %}
```

Contoh:

{% for order_status in order_statuses %}
  SUM(
      CASE WHEN status = '{{ order_status }}' 
        THEN order_id 
      END)
{% endfor %}

Pernyataan Jinja: loop

SQL berulang:

SELECT 
    user_id,
    SUM(CASE WHEN status = 'Shipped' THEN 1 ELSE 0 END) 
        AS num_orders_Shipped,
    SUM(CASE WHEN status = 'Complete' THEN 1 ELSE 0 END) 
        AS num_orders_Complete,
    SUM(CASE WHEN status = 'Processing' THEN 1 ELSE 0 END) 
        AS num_orders_Processing,        
FROM {{ ref('stg_looker__orders') }}
GROUP BY 1

Pernyataan Jinja: loop

{% set order_statuses = ['Shipped', 'Complete', 'Processing'] %}

SELECT 
    user_id,
    -- Loop Jinja
    {% for order_status in order_statuses %}
        SUM(CASE WHEN status = '{{ order_status }}' THEN 1 ELSE 0 END) 
        -- Nama kolom terparametrisasi
        AS num_orders_{{ order_status }}
    {% endfor %}
FROM {{ ref('stg_looker__orders') }}
GROUP BY 1

Pernyataan Jinja: loop

Keluaran dbt compile:

SELECT 
    user_id,
    SUM(CASE WHEN status = 'Shipped' THEN 1 ELSE 0 END) 
        AS num_orders_Shipped,
    SUM(CASE WHEN status = 'Complete' THEN 1 ELSE 0 END) 
        AS num_orders_Complete,
    SUM(CASE WHEN status = 'Processing' THEN 1 ELSE 0 END) 
        AS num_orders_Processing,        
FROM "dbt"."main"."stg_looker__orders"
GROUP BY 1

Pernyataan Jinja: macro

Sebuah macro Jinja:

Adalah fungsi, ditulis dalam Jinja
Dapat digunakan ulang
Disimpan di folder /macros

COALESCE():

mengembalikan nilai pertama yang bukan null
sintaks: COALESCE(value1, value2, ...)
mis. COALESCE(nickname, first_name)

Contoh fungsi macro:

Tangkapan layar IDE dengan file `coalesce_and_round.sql` terbuka menampilkan logika macro-nya.

Pernyataan Jinja: macro

Pernyataan Jinja berada dalam {% %}:

Fungsi macro yang dapat digunakan ulang:

Templat:
```
{% macro ... %} ... {% endmacro %}
```

Contoh:

{% macro coalesce_and_round(column_name, decimal_places = 2) %}
      ROUND(COALESCE({{ column_name }}, 0), {{ decimal_places }})
{% endmacro %}

Pernyataan Jinja: macro

SQL berulang

ROUND(COALESCE(sales_amount, 0), 2) AS sales_amount,
ROUND(COALESCE(cost_of_goods_sold, 0), 2) AS cost_of_goods_sold,

DRY (Don't Repeat Yourself)

Buat macro bernama coalesce_and_round.sql
Simpan di /macros

Panggil:

{{ coalesce_and_round('sales_amount', 2) }} AS sales_amount,
{{ coalesce_and_round('cost_of_goods_sold', 2) }} AS cost_of_goods_sold,

Mengelola whitespace Jinja

Seperti ditulis:

{% set traffic_source_values = ['Adwords', 'Email', 'Facebook'] %}
{% set browser_values = ['Chrome', 'Firefox', 'Safari', 'IE', 'Other'] %}

SELECT 
    user_id,
    COUNT(DISTINCT session_id) AS num_web_sessions,
...

Mengelola whitespace Jinja

Hasil kompilasi:




SELECT 
    user_id,
    COUNT(DISTINCT session_id) AS num_web_sessions,
...

Mengelola whitespace Jinja

{%- ... %} menghapus whitespace sebelum.
{% ... -%} menghapus whitespace setelah.
{%- ... -%} menghapus keduanya.
Contoh:

{%- set traffic_source_values = ['Adwords', 'Email', 'Facebook'] -%}
{%- set browser_values = ['Chrome', 'Firefox', 'Safari', 'IE', 'Other'] -%}

SELECT 
    user_id,
    COUNT(DISTINCT session_id) AS num_web_sessions,
...

Ayo berlatih!

Studi Kasus: Membangun Model Data E-Commerce dengan dbt