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Análisis dimensional

Análisis dimensional. Aplicaciones del Análisis de Datos: Formular queries Extraer datos aggregados Analizar resultados Visualizar resultados

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Análisis dimensional

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  1. Análisis dimensional • Aplicaciones del Análisis de Datos: • Formular queries • Extraer datos aggregados • Analizar resultados • Visualizar resultados • El conjunto de datos se representa como un espacio n-dimensional. La reducción dimensional se ejecuta mediante la sumarización sobre las dimensiones que son dejadas de lado

  2. Ejemplo • Ventas (storeId,itemId,timeId,…,monto) • Store(storeId,nombre,region,pais,ciudad) Sumarizar por region: SELECT region,sum(monto) FROM Ventas V, Store S WHERE V.sotreId=S.storeId GROUP BY region

  3. Sumarización • Un problema n-dimensional se representa en un archivo de 2 dimensiones, con n dominions de atributos. • Ej.: Clima(tiempo,lat.long,altit,temp, presion) 4 dimensiones, 2 medidas.

  4. Problemas del Group By • Es complicado para : • Histogramas • Roll-up • Subtotales, drill-dpown • Cross-tabs

  5. Problemas (cont.) • Histogramas • SELECT day,pais,max(temp) FROM ( SELECT day(time) as day, nation (lat,long) as pais FROM clima) as foo Group by day,pais Primero debe armar la tabla y luego agrupar.

  6. Roll-up/drill-down Roll-Up

  7. Solución en SQL

  8. Problema • Aumento de la cantidad de columnas • P.ej: 6 dimensiones =>64 columnas • Alternativa: introducir un valor “ALL”. El nro de columnas permanece constante

  9. Data Cube

  10. Data Cube (cont.)

  11. Data Cube (cont.)

  12. Operador CUBE en SQL SELECT “ALL”, “ALL, “ALL”, SUM (ventas) FROM Sales UNION SELECT Modelo, “ALL, “ALL”, SUM (ventas) FROM Sales GROUP BY Modelo UNION SELECT Modelo, “ALL”,Color, SUM (ventas) FROM Sales GROUP BY Modelo,Color UNION ……

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