Fonctions de fenêtre

SQL Server intermédiaire

Ginger Grant

Instructor

Fonctions de fenêtrage

Regrouper des données en T-SQL

SELECT SalesPerson, SalesYear, 
       CurrentQuota, ModifiedDate
FROM SaleGoal
WHERE SalesYear = 2011

+------------+----------+---------------+----------------+
|SalesPerson |SalesYear | CurrentQuota  | ModifiedDate   |
+------------+----------+---------------+----------------+
| Bob        | 2011     | 28000.00      | 2011-04-16     |
| Bob        | 2011     |  7000.00      | 2011-07-16     |
| Bob        | 2011     | 91000.00      | 2011-10-16     |
| Mary       | 2011     |367000.00      | 2011-04-16     |
| Mary       | 2011     |556000.00      | 2011-07-16     |
| Mary       | 2011     |502000.00      | 2011-10-16     |
+------------+----------+---------------+----------------+

Syntaxe des fenêtres en T-SQL

Créez la fenêtre avec la clause OVER
PARTITION BY définit la plage
Sans PARTITION BY, la plage couvre toute la table
Pour ordonner les résultats, utilisez ORDER BY
Permet d'agréger en même temps que la fenêtre

. . . 
-- Créer un regroupement de données par fenêtre
OVER (PARTITION BY SalesYear ORDER BY SalesYear)

Fonctions de fenêtre (SUM)

SELECT SalesPerson, SalesYear, CurrentQuota, 
       SUM(CurrentQuota) 
       OVER (PARTITION BY SalesYear) AS YearlyTotal, 
       ModifiedDate AS ModDate
FROM SaleGoal

+------------+----------+-------------+------------+----------+
|SalesPerson |SalesYear |CurrentQuota |YearlyTotal | ModDate  |
+------------+----------+-------------+------------+----------+
|Bob         |2011      |28000.00     |1551000.00  |2011-04-16|
|Bob         |2011      |7000.00      |1551000.00  |2011-07-17| 
|Mary        |2011      |367000.00    |1551000.00  |2011-04-16|
|Mary        |2011      |556000.00    |1551000.00  |2011-07-15|
|Bob         |2012      |70000.00     |1859000.00  |2012-01-15|
|Bob         |2012      |154000.00    |1859000.00  |2012-04-16|
|Bob         |2012      |107000.00    |1859000.00  |2012-07-16|
...          |          |             |            |          |
+------------+----------+-------------+------------+----------+

Fonctions de fenêtre (COUNT)

SELECT SalesPerson, SalesYear, CurrentQuota, 
       COUNT(CurrentQuota) 
       OVER (PARTITION BY SalesYear) AS QuotaPerYear, 
       ModifiedDate AS ModDate
FROM SaleGoal

+------------+----------+------------+--------------+----------+
|SalesPerson |SalesYear |CurrentQuota|QuotaPerYear  | ModDate  |
+------------+----------+------------+--------------+----------+
|Bob         |2011      |28000.00    |4             |2011-04-16|
|Bob         |2011      |7000.00     |4             |2011-07-17| 
|Mary        |2011      |367000.00   |4             |2011-04-16|
|Mary        |2011      |556000.00   |4             |2011-07-15|
|Bob         |2012      |70000.00    |8             |2012-01-15|
|Bob         |2012      |154000.00   |8             |2012-04-15|
|Bob         |2012      |107000.00   |8             |2012-10-16|
...
+------------+----------+------------+------------+----------+

Remarquez que le compte repart à zéro pour chaque fenêtre dans la colonne QuotaPerYear.

Passons à la pratique !

SQL Server intermédiaire