PL-300 · 1.3.6 · Prepare the data
Fact and dimension tables
Create fact tables and dimension tables
Dimensions describe entities; facts record measurable events and reference dimensions by key.
See the star
A separates measurable business events from the descriptive entities used to filter them. The sits in the center with repeated dimension keys and . contain unique keys and descriptive attributes.
Read the relationship
Ask what one row represents. A fact row normally represents an event or observation and repeats dimension keys. A dimension row represents one entity and has a unique key used for filtering and grouping.
In the common one-to-many pattern, the dimension is on the one side and the fact is on the many side. and tell you more than table size or naming.
Exam clue: the one side is normally the dimension; the many side is normally the fact.
Key points
- Dimension: unique key and descriptive attributes
- Fact: repeated dimension keys and
- : dimension is usually the one side
- : facts connect to surrounding dimensions
Click an underlined term for a one-line explanation, or see them all in the glossary .
Exam trap
Table size does not define fact or dimension roles; does.
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