Contents
Do dates go in fact tables?
Fact tables may include multiple dates per record. For instance, a record can have an open date, a closed date, an updated date etc.
Are dates facts or dimensions?
Typically dimensions in a data warehouse are organized internally into one or more hierarchies. “Date” is a common dimension, with several possible hierarchies: “Days (are grouped into) Months (which are grouped into) Years”, “Days (are grouped into) Weeks (which are grouped into) Years”
What is factless fact table with example?
A factless fact table is a fact table that does not have any measures. It is essentially an intersection of dimensions (it contains nothing but dimensional keys). There are two types of factless tables: One is for capturing an event, and one is for describing conditions.
Can a surrogate key be a primary key?
In a current database, the surrogate key can be the primary key, generated by the database management system and not derived from any application data in the database. The only significance of the surrogate key is to act as the primary key.
What is date dimension and how will you load date dimension?
Date Dimension is a table that has one record per each day, no more, no less! Depends on the period used in the business you can define start and end of the date dimension. For example your date dimension can start from 1st of Jan 1980 to 31st of December of 2030.
What is a role playing dimension?
A table with multiple valid relationships between itself and another table is known as a role-playing dimension. This is most commonly seen in dimensions such as Time and Customer. Decide how to use these roles with other facts that do not share the same concepts. …
What is factless fact table?
Why a factless fact table is used?
In conclusion, factless fact tables are important dimensional data structures use to convey transactional information which contain no measures. These tables are occasionally necessary for capturing important dimensional relationships which are critical to the meeting the defined business reporting requirements.
How to deal with nulls in a report?
Putting a null in these fields can be confusing to the user, as it will appear as a blank on reports and pull-down menus, and require special query syntax to find. Instead, we recommend substituting an appropriately descriptive string, like “Unknown” or “Not provided.”
What happens if you null ship _ date in dimensional model?
In this case, Ship_Date is a foreign key to the date dimension table, but will not join as users expect if we leave the value as null. That is, any fact reporting from the date table joined on Ship_Date will exclude all orders with a null Ship_Date.
Why are nulls confusing in a data warehouse?
Nulls can confuse both data warehouse developers and users because the database treats nulls differently from blanks or zeros, even though they look like blanks or zeros. This design tip explores the three major areas where we find nulls in our source data and makes recommendations on how to handle each situation.
When do you leave a null value in a function?
In this case, the null value has two potential meanings. Either the value did not exist, or our measurement system failed to capture the value. Either way, we generally leave the value as null because most database products will handle nulls properly in aggregate functions including SUM, MAX, MIN, COUNT, and AVG.