You can identify a dimension (for example, Year) as a time dimension. At least one level of a time dimension must have a chronological key. The following is a list of some guidelines you should use when setting up and using time dimensions:
- At least one level of a time dimension must have chronological key. For more information, see Selecting and Sorting Chronological Keys in a Time Dimension.
- All time series measures using the Ago and ToDate functions must be on time levels. Ago and ToDate aggregates are created as derived logical columns. For information, refer to About Time Series Conversion Functions.
- Any physical table that is part of a time logical table cannot appear in another logical table. This prevents using date fields from calendar table as measures.
- Physical tables in time sources, except the most detailed ones, cannot have joins to table outside their source. The join has to be between the time table and the fact table. The join can only be based on foreign key; it cannot be a complex join.
- Ago or ToDate functionality is not supported on fragmented logical table sources. For more information, refer to About Time Series Conversion Functions.