Skip to main content

Fact & Dimension tables

By

Fact and Dimension table what does it mean? How do we classify which is fact and dimension table? Where do we use these. These are some of the most common questions that pop up when we hear dimension and fact table.

Going by book, Fact and Dimension table in technical perspective is defined as follows

The fact table contains business facts (or measures), and foreign keys which refer to candidate keys (normally primary keys) in the dimension tables.

A dimension table is a table in a star schema of a data warehouse. A dimension table stores attributes, or dimensions, that describe the objects in a fact table.

Not let’s dig into this we have basically two schemas Star and Snow Flake schema

In Star schema  a fact table is surrounded by dimension tables. In Snow flake schema we have again Fact table in the center of schema  surrounded by dimension tables, however in here the dimension tables can have their own child tables.

facts correspond to events, dimensions correspond to people, items, or other objects. For example, in the retail scenario, Purchases, returns and calls are facts. On the other hand, customers, employees, items and stores are dimensions .

  

 
                                               

Comments

Post a Comment

Popular posts from this blog

Comparing Objects in Informatica

By
We might face a scenario where there may be difference between PRODUCTION v/s SIT version of code or any environment or between different folders in same environment. In here we go for comparison of objects we can compare between mappings,sessions,workflows In Designer it would be present under "Mappings" tab we can find "Compare" option. In workflow manger under "Tasks & Workfows" tab we can find "Compare" option for tasks and workflows comparison respectively. However the easiest and probably the best practice would be by doing using Repository Manager.In Repository Manager under "Edit" tab we can find "Compare" option. The advantage of using Repository manager it compares all the objects at one go i.e. workflow,session and mapping. Hence reducing the effort of individually checking the mapping and session separately. Once we select the folder and corresponding workflow we Can click compare for checking out ...
11 comments
Read more

Types of Joins in Oracle/Teradata

By Anonymous
In Data warehousing, irrespective of schema (snow flake schema or star schema) we are using, we should join dimension and fact tables to analyze the business. Below are the frequently used joins: Inner join Left outer Join Right outer Join Cross join Inner Join: Inner join will give you the matching rows from both the tables. If the join condition is not matching then zero records will return. We should use ON keyword to give join condition. Example: Table1: ID Name 1 Krishna 2 Anirudh 4 Ashok Table2: ID Location 1 Bangalore 3 Chennai 4 Chennai We can join above two tables using inner join based on key column ID. SELECT T1.ID, T1.Name, T2.Location FROM Table1 T1 INNER JOIN Table2 T2 ON T1.ID = T2.ID     If we are using inner join, it will give us matching rows from both the table. Here in this example, we have 2 matching rows i.e. ID 1 and 4. Below will be the result set for the above exa...
Post a Comment
Read more

Looping using Expression Transformation in Informatica

By
One of the most common used transformation in Informatica is Expression transformation. In Expression transformation we can perform various operations such as data conversions i.e to_date,to_char, string manipulation such as substr,instr etc. Now coming to one of the widely and prominent task which we perform using Expression transformation is looping a value. Expression transformation has three types of ports i.e. input,variable and output.Only output port values can be propagated to next transformations. So in order to pass values of input and variable ports to next level of transformation these must be assigned to output ports.The order of execution in Expression transformation is top to bottom and first input then variable and finally output ports are processed. let us consider the following scenario   The files should be generated with employee name as file name and that particular file should have the details of that respective employee only, if the employee has more t...
1 comment
Read more