ROLLUP

Toma de decisiones basada en datos en SQL

Bart Baesens

Professor Data Science and Analytics

Tabla renting_extended

Las primeras filas de la tabla « renting_extended » (Recursos de la red):

| renting_id | country  | genre  | rating |
|------------|----------|--------|--------|
| 2          | Belgium  | Drama  | 10     |
| 32         | Belgium  | Drama  | 10     |
| 203        | Austria  | Drama  | 6      |
| 292        | Austria  | Comedy | 8      |
| 363        | Belgium  | Drama  | 7      |
| .......... | ........ | ...... | ...... |

Consulta con ROLLUP

SELECT country, 
       genre, 
       COUNT(*)
FROM renting_extended
GROUP BY ROLLUP (country, genre);

Niveles de agregación
- Agregación de cada combinación de país y género
- Agregación solo por país
- Agregación total

Consulta con ROLLUP

SELECT country, 
       genre, 
       COUNT(*)
FROM renting_extended
GROUP BY ROLLUP (country, genre);

| country | genre  | count |
|---------|--------|-------|
| null    | null   | 22    |
| Austria | Comedy | 2     |
| Belgium | Drama  | 15    |
| Austria | Drama  | 4     |
| Belgium | Comedy | 1     |
| Belgium | null   | 16    |
| Austria | null   | 6     |

Ordenar en ROLLUP

SELECT country, 
       genre, 
       COUNT(*)
FROM renting_extended
GROUP BY ROLLUP (genre, country);

| country | genre  | count |
|---------|--------|-------|
| null    | null   | 22    |
| Austria | Comedy | 2     |
| Belgium | Drama  | 15    |
| Austria | Drama  | 4     |
| Belgium | Comedy | 1     |
| null    | Comedy | 3     |
| null    | Drama  | 19    |

Resumen

Devuelve agregados para una jerarquía de valores, por ejemplo: ROLLUP (country, genre)
- Alquiler de películas por país y género
- Alquiler de películas para cada país
- Número total de alquileres de películas
En cada paso, se omite un nivel de detalle.
El orden de los nombres de las columnas es importante para ROLLUP

Número de alquileres y valoraciones

SELECT country, 
       genre, 
       COUNT(*) AS n_rentals,
       COUNT(rating) AS n_ratings
FROM renting_extended
GROUP BY ROLLUP (genre, country);

| country  | genre  | n_rentals | n_ratings |
|----------|--------|-----------|-----------|
| null     | null   | 22        | 9         |
| Belgium  | Drama  | 15        | 6         |
| Austria  | Comedy | 2         | 1         |
| Belgium  | Comedy | 1         | 0         |
| Austria  | Drama  | 4         | 2         |
| null     | Comedy | 3         | 1         |
| null     | Drama  | 19        | 8         |

¡Vamos a practicar!

Toma de decisiones basada en datos en SQL