Dimension Table Vs Fact Table

What is the main difference in the logic when you create a mapping for a dimension table with that of a fact table in Informatica.

Questions by goutamhere2interact

Showing Answers 1 - 14 of 14 Answers

dwhlabs

  • Jul 23rd, 2008
 

Dimension Table features

1. It provides the context /descriptive information for a fact table measurements.
2. Provides entry points to data.
3. Structure of Dimension - Surrogate key , one or more other fields that compose the natural key (nk) and set of Attributes.

4. Size of Dimension Table is smaller than Fact Table.

5. In a schema more number of dimensions are presented than Fact Table.

6. Surrogate Key is used to prevent the primary key (pk) violation(store historical data).

7. Values of fields are in numeric and text representation.

Fact Table features

1. It provides measurement of an enterprise.

2. Measurement is the amount determined by observation.

3. Structure of Fact Table - foreign key (fk), Degenerated Dimension and Measurements.

4. Size of Fact Table is larger than Dimension Table.

5. In a schema less number of Fact Tables observed compared to Dimension Tables.

6. Compose of Degenerate Dimension fields act as Primary Key.

7. Values of the fields always in numeric or integer form.

 

I think there won't be any logic difference in a mapping to load dimension table & fact table.  We can load the dimension table directly but we can't load the fact table first. So, to load the fact table we need to load the dimension table first. Also while loading the fact table we will make a lookup on the dimensioin table, cause the fact table contains the measures/facts & the foreign keys which are primary keys in the dimension tables surrounded to that fact table. We can load the dimension table & fact table in one mapping by using the "Target Load Order/Target Load Plan" in informatica.

Example:

                                            / Target 1 (Dimension Table)
Source - Transformations -
                                            Target 2 (Fact Table)

etc.....

The main difference between dimension and the fact table is that Dimension preserves the historical data (like in case of type2) we will have to use update strategy and other transformations to make that happen but fact will be a direct load with few one or more lookups from the dimension and also since the fact and dimenision has the foriegn key relationship the dimension has to be loaded first before the fact

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Kadhirvelu

  • Oct 23rd, 2008
 

Dimensions are particular angle or perspective that you see the facts i.e aggregates or measures. as mentioned in previous replies, facts cannot be loaded unless until dimensions got loaded.

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sahan

  • Jul 16th, 2009
 

You can load the dimension table directly, but you cannot load the fact table directly, You need to look up the dimension table, b'coz fact tables contains foreign keys, which are the primary keys in dimension table. You can load the dimensions and facts into one mapping using target load plan.

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Karin Divens

  • Aug 19th, 2011
 

.. But you are aware of the fact that the Target Load Order is only available if you have different pipelines, right?

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The data in the dimensions table is generally static and descriptive. The fact table contains two columns one is foreign key and the other fact data generally the data in the fact tables contains numeric data

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Difference between dimension and fact tables
1) dimension data is denormalized where as fact table contains normalized data
2)dimension table contains many columns where as fact table contains less columns only 2 in fact
3) the data in the dimension tables are less compared to the data in the fact tables
4) The data in the dimension table is static and descriptive in nature where as the fact table contains numeric and will change regularly
5) dimension tables generally called as lookup or reference table as well. facts tables are the key performance indicators of the business

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JEEVAN KUMAR

  • Nov 18th, 2011
 

Dimension table:::>it contains denormalized data and it takes less memory because in which we have more no.of columns and less no.of records.
fact table::::> it contains normalized data and it takes more memory because in which we have less no.of columns and more no.of records(i mean it maintains historical data)

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Nitin

  • Nov 30th, 2011
 

Please specify the definition sir

Code
  1. printf("hid");

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ASHU

  • Jan 21st, 2012
 

A Dimension table contain descriptive (detailed) data and a fact table contain measurements (facts) which are used to evaluate a business, all numeric are not a facts but the numeric which are key performance indicators is known as facts.. fact table contain summarized data....
ASHU (KARIMNAGAR)

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Amar

  • Nov 30th, 2012
 

The main logical difference is that we use connected lookup while loading dimensions and unconnected look up while loading facts

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