Summarizability Patterns for Dimension Tables

Lesson Objectives
Recognize data patterns with dimension summarizability problems
Recognize cardinalities in schema designs for dimension summarizability problems
Explain ways to resolve dimension summarizability problems

Summarizability Motivation
Summary computations in navigation and join operations
Violations of summarizability
Incorrect results
Erroneous decision making and user confusion
Inability to use performance optimizations
Relationships among dimension levels and dimension and fact tables

Drill Down Incompleteness Example
Drill down

Roll-up Incompleteness Example
Rollup

Non Strict Example
Rollup

Dimension Non Summarizability Patterns

Dimension Non Summarizability Examples

Resolving Dimension Problems
Drill-down and roll-up problems due to exceptions
Incomplete drill down: add connection to unallocated children
Incomplete rollup: add connection to unallocated parent
Non strict relationship (M-N) among dimensions
Design error
Use separate hierarchies or a major parent category

Summary
Importance of understanding summarizability problems
Incomplete hierarchical dimension relationships
Non strict relationships among hierarchy levels
Tedious to discover and resolve