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School of Information and Communication Technology. Royal Institute of Technology Stockholm, Sweden. Ralph Kimball, Kimball Group, Number 51, February 1 2004. Latest thinking on Time Dimension Tables. Calendar Date Dimension. Most common and useful time dimension

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calendar date dimension
Calendar Date Dimension
  • Most common and useful time dimension
  • Completely specified at the beginning
  • Attributes
    • Generated directly: month name, year, etc.
    • Embedded: holidays, fiscal periods, etc.
    • Date Type, Full Date
    • Surrogate vs. smart keys
date type full date
Date Type, Full Date
  • “NA”, null
  • “date”, 20081125
  • “date”, 20081126
  • “date”, 20081127
surrogate vs smart keys
Surrogate vs. smart keys
  • Surrogate Keys
    • 1, “NA”, null
    • 329, “date”, 20081125
    • 330, “date”, 20081126
    • 331, “date”, 20081127
  • * assuming we count 2008 onwards
surrogate vs smart keys1
Surrogate vs. smart keys
  • Smart Keys
    • 99999999, “NA”, null
    • 20081125, “date”, 20081125
    • 20081126, “date”, 20081126
    • 20081127, “date”, 20081127
time of day
Time of day
  • Previous approach
    • Date Dimension (year, month, week, day, etc.)
    • Time Dimension (hour, minutes, seconds, etc.)
  • Time of day
    • Time-of-day Dimension(minutes or seconds past midnight)
  • New approach
    • Date Dimension
    • New Fact – SQL Date Timestamp
    • Time-of-day Dimension (optional)