OLAP-operationer: GROUPING SETS

Datadriven beslutsfattning i SQL

Irene Ortner

Data Scientist at Applied Statistics

Översikt över OLAP-operatorer i SQL

SQL-tillägg för OLAP-operationer

GROUP BY CUBE
GROUP BY ROLLUP
GROUP BY GROUPING SETS

Tabellen renting_extended

De första raderna i tabellen renting_extended:

| 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      |
| .......... | ........ | ...... | ...... |

GROUP BY GROUPING SETS

Exempel på en fråga med operatorn GROUPING SETS:

SELECT country, 
       genre, 
       COUNT(*)
FROM rentings_extended
GROUP BY GROUPING SETS ((country, genre), (country), (genre), ());

Kolumnnamn inom parentes utgör en aggregeringsnivå.
GROUP BY GROUPING SETS returnerar en UNION av flera GROUP BY-frågor.

GROUPING SETS och GROUP BY-frågor

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

Räkna uthyrningar per unik kombination av land och genre.
Uttryck i GROUPING SETS: (country, genre)

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

| country | genre  | count  |
|---------|--------|--------|
| Austria | Comedy | 2      |
| Belgium | Drama  | 15     |
| Austria | Drama  | 4      |
| Belgium | Comedy | 1      |

GROUPING SETS och GROUP BY-frågor

SELECT country, COUNT(*)
FROM renting_extended
GROUP BY GROUPING SETS (country);

Räkna uthyrningar per land.
Uttryck i GROUPING SETS: (country)

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

| country | count |
|---------|-------|
| Austria | 16    |
| Belgium | 6     |

GROUPING SETS och GROUP BY-frågor

SELECT genre, COUNT(*)
FROM renting_extended
GROUP BY GROUPING SETS (genre);

Räkna uthyrningar per genre.
Uttryck i GROUPING SETS: (genre)

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

| country | count |
|---------|-------|
| Comedy  | 3     |
| Drama   | 19    |

GROUPING SETS och GROUP BY-frågor

SELECT COUNT(*)
FROM renting_extended
GROUP BY GROUPING SETS ();

Total aggregering – räkna alla uthyrningar.
Uttryck i GROUPING SETS: ()

SELECT COUNT(*)
FROM renting_extended;

| count |
|-------|
| 22    |

Notation för GROUP BY GROUPING SETS

GROUP BY GROUPING SETS (...)

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

UNION av de 4 föregående frågorna.
Samlar all information från en pivottabell i en enda fråga.
Motsvarar GROUP BY CUBE (country, genre).

Resultat med operatorn GROUPING SETS

SELECT country, genre, COUNT(*)
FROM renting_extended
GROUP BY GROUPING SETS ((country, genre), (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   |
| NULL    | Comedy | 3   |
| NULL    | Drama  | 19  |

Beräkna antal uthyrningar och genomsnittligt betyg

Kombinera utvalda aggregeringar:
- land och genre
- genre

Använd antal uthyrningar och genomsnittliga betyg för aggregeringen.

SELECT country, 
     genre, 
     COUNT(*), 
     AVG(rating) AS avg_rating
FROM renting_extended
GROUP BY GROUPING SETS ((country, genre), (genre));

Beräkna antal uthyrningar och genomsnittligt betyg

SELECT country, genre, COUNT(*), AVG(rating) AS avg_rating
FROM renting_extended
GROUP BY GROUPING SETS ((country, genre), (genre));

| country | genre  | count| avg_rating |
|---------|--------|------|------------|
| Austria | Comedy | 2    | 8.00       |
| Belgium | Drama  | 15   | 9.17       |
| Austria | Drama  | 4    | 6.00       |
| Belgium | Comedy | 1    | NULL       |
| NULL    | Comedy | 3    | 8.00       |
| NULL    | Drama  | 19   | 8.38       |

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