Les conditions

CASE..WHEN..THEN..ELSE..

case when dt < '2024-01-01' then 1.18 else 1.10 end

Cela ressemble à l'expression ternaire dans les langages de programmation classiques.

Catégoriser des dates

case
    when dt < '2023-08-01' then '1. Avant'
    when dt < '2023-09-01' then '2. Pendant'
    when dt >= '2023-09-01' then '3. Apres' 
end periode

Segementer la base client suivant les montants d'achats

case
    when total_amount > 0 and total_amount < 5000 then 'LVC'
    when total_amount >= 5000 and total_amount < 70000 then 'MVC'
    when total_amount >= 70000 then 'HVC'
else 'Inactive' end   as segment

```sql title = "Pivot Table" select dt, sum(case when product_category = 'Data Package' then amount else 0 end) data_pack_amount, sum(case when product_category = 'Voice Package' then amount else 0 end) voice_pack_amount, sum(case when product_category = 'Voice & Data Package' then amount else 0 end) mix_pack_amount, sum(case when product_category = 'Communication Credit' then amount else 0 end) credit_amount, sum(case when product_category = 'Other' then amount else 0 end) other_amount from edw.fct_orders where dt = rundt group by 1

## Structure conditionnelle `IF..THEN..`
La structure conditionnelle `IF` permet d'exécuter des instructions lorsqu'une condition est vérifiée.
```sql title="Structure conditionnelle"  linenums="1"
do
$$
declare
    age integer;
begin
    age := 35;
    if age >= 18 then
        raise info 'You are major !';
    end if;
end;
$$;

Structure alternative

do
$$
declare
    age integer = 35;
begin
    if age >= 18 then
        raise info 'You are major !';
    else
        raise info 'You are minor !';
    end if;
end;
$$;

Structure conditionnelle imbriquée

Dans le cadre de problèmes complexes, il peut être nécessaire

do
$$
declare
    age integer = 35;
begin
    if age >= 25 then
        raise info 'You are adult !';
    elif age >= 18 then
        raise info 'You are major !';
    else
        raise info 'You are minor !';
    end if;
end;
$$;

Conditions imbriquées

Dans le cadre de problèmes complexes, il peut être nécessaire

do
$$
declare
    age integer = 35;
begin
    if age >= 18 then
        raise info 'You are major !';
    else
        raise info 'You are minor !';
    end if;
end;
$$;

Applications

if rundt >= '2024-01-01' then
    drop table if exists tmp.store_orders_stg;
    create table tmp.store_orders_stg as (
        select *
        from prod.store_orders t
        where order_date >= rundt
            and order_date < rundt + 1
    );
else
    drop table if exists tmp.store_orders_stg;
    create table tmp.store_orders_stg as (
        select *
        from stagging.orders t
        where order_date >= rundt
            and order_date < rundt + 1
    );
end if;

Arrêter l'execution pour certaines plages d'heures par exemple

if not (to_char(now(), 'HH24') between '06' and '20') then
    return 'N';
end if;

Arrêter l'execution lorsque les données source ne sont pas disponibles

--- Compter le nombre de lignes
select count(*)
into _cnt
from tmp.store_orders_stg
where dt = rundt;

if _cnt = 0 then
    raise notice 'Data not found !';
    return 'N';
end if;

---

.