How do you load a fact table?

How do you load a fact table?

Fact tables are normally loaded from transaction tables such as order tables or from transactional files, such as web logs. Hence the number of rows to update or insert in a load is much larger than in dimensions. The core of loading fact tables is to change the natural keys into surrogate keys.

How do you populate a fact table?

The way I populate a fact is:

1. Load the facts into a staging table.
2. The staging table has additional columns which contain your surrogate keys.
3. Run an update statement on your staging table that fills in the surrogate keys.
4. Pick an appropriate window in your fact. Delete and reload that window.

Can you load fact table before dimension?

The process of loading the base schema requires that fact tables and dimension tables be loaded. Fact tables bear foreign keys to the dimension tables and are therefore dependent entities. This would suggest that dimension tables be loaded first.

How are loading fact tables different from loading dimensions?

Loading fact tables is very different than loading dimensions. First, we need to know the type of fact we are using. The major types of facts are transaction, periodic snapshot, accumulating snapshot and time-span accumulating snapshots. We also need to know the grain of the fact, the dimensional keys which are associated to the measurement event.

How are fact tables loaded in data warehouse?

Populating Fact Tables (Data Warehouse Loading Part 3) Fact tables are normally loaded from transaction tables, such as order tables. Or from transactional files, such as web logs. Hence the number of rows to update in a load is much larger than in dimensions.

When to use SSIs for fact table loading?

When dealing with large volumes, you may need to handle partition inserts and deal with updates in a different way. In general, fact table loading involves a few common tasks: Preparing your source data to be at the same granularity as your fact table, including having the dimension business keys and measures in the source data

What’s the rule of thumb for a fact table?

A good rule of a thumb is that we consider anything under 2% very sparse; anything above that is not so sparse. This is the simplest and most common type of fact table. The grain of this type is one row per transaction, or one row per line on a transaction.