Data Warehousing Interview Questions
Which type of relation between fact and dimension table in star schema and snowflake schema?Like one to one or many to many?
For one dimension record, you will see many fact records associated.Many to one or one to many relationship is not to be confused with number of records or columns in a table. that has nothing to do with a relation
Fact to dimension is many to one...for one dimension record, you will see many fact records associated
Diff between primary index and primary key
What is the main difference between primary index and primary key in teradata? And can we have this two on same column?
If i am not wrong , both the titles should be swapped from the above answer as follows , Primary Key --Always Unique --Does not allow NULL values --Optional for a table --Values cant be updated --Doe...
Primary Index --Always Unique --Does not allow NULL values --Optional for a table --Values can’t be updated --Does not allow Duplicates --Does not choose best access path --Used In Joins Primary Ke...
What are the various olap & molap operations?
olap means online analytical processing its mainly used for ssas and then molap means multidimensional online analytical processing its different to olap
If two co>os are interacting with each other what parameters should we have to set.
You can interact with another co-operating system with setting below parameters in .abinitiorc of existing coperating system : AB_NODE : Node at which this another co-operating system resides AB_HOME...
Can we write the date in sand box parameter in detail explain how to do that?
In Informatica v 8.6 one workflow triggers another workflow. how where do we put a distinct clause so that the duplicates are not reflected in the report formed by the second wf. First wf does a partial load
Your question is not very clear. However, if you mean to say that you are loading the same target table using two different mappings, then here is the answer. You can use any one of the below approach...
3.Surrogate key is a sequencer which is used to uniquely identify a row in a OLAP. This helps in implementing SCD Type 2 in data warehousing.
OLAP:
1). Store historical data of an organization
2). Data is used for BI/ business strategic decision
OLTP
1). Real time transactional data
2). Data is used to have track of transaction details.
Replicating the record in target in Informatica.
My source is like: sno name 1 xxxx 2 yyyy i want the target like: sno name frequency 1 xxxx 1 2 yyyy 2 2 yyyy 2 how can I replicate the "2 yyyy". i am supposed to make it dynamic for all possible frequencies.
What are the types of slowly changingdimension ?Can you explain please types of slowly changingdimension in detail ?
Slowly changing dimensions are 3 types. In scd-1 new data is inserted by deleting old one. so latest information is stored. In scd-2 we can maintain history of data for a particular item. new data is...
SCD are of following types: type 1 - updates changes without preserving history type 2 - stores history data by maintaining versions of the updated data type 3 - either stores current and previous ver...
How to create sequencer in datastage(parallel)?
What is the purpose of sequencer and how to create in real time project in parallel?
How do we increase hash file size?
How do we increase hash file size?
Fan trap: one of the schema-tables in your physical realization via an rdbms has a 1:many relationship between two slave-tables but there is no path between the two slave tables! So we are clueless ab...
A fan trap is a many-to-many relationship between two fact tables, bridged by a dimension.
What is the difference between aggregate table and materliazed view?
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Editorial / Best Answer
Answered by: joshmohit
Member Since Oct-2010 | Answered On : Nov 3rd, 2010
Aggregate table is a generic term to represent the summaries built in a warehouse. MAterilaized view is the technical implementation of these aggregate tables. Though, Materialized views come with the database specific properties which might not be covered with the generic definition of aggregate tables.
An aggregate table is a table that contains data that is summarized somehow, for example, it contains a summary of Customer by Product by Week. A more granular level of detail would be the transactio...
Aggregate table is a generic term to represent the summaries built in a warehouse. MAterilaized view is the technical implementation of these aggregate tables. Though, Materialized views come with the...
How can I load rejected data file? is it necessary to create new mapping for that.....How can I load by reject data utility explain me clearly
What are the advantages of data mining over traditional approaches>
Data mining is nothing about analyzing the results with different prospects.
Relational and dimensional data modeling
How can you say relational is normalized one and data warehouse i.E dimensional modeling is de-normalized one when both model follows the primary key concept in its table to store data
Data obtain from transactional source which is normalized on 3NF. It has been staged and demoralized the data and after denationalization of data re-normalized on 2NF and 3NF. Therefore, It is called Demoralized but it is normalized not like the transactional
Dimensional modeling usually does with 2NF for dimensions and 3NF for facts.
Dimensions are de-normalized for better query performance and for better understanding by business users.
What is the difference between Oracle and teradata?
Teradata and Oracle produce relational database management systems. What the previous answers do not provide are important facts about both platforms. Teradata products are a "combo" of hardware + so...
Oracle and Teradata are RDBMS databases. But the main difference is Terdata supports parallelism and it allows more data 10 to power 12 Gb where it increases scability when compared to Oracle
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There are following types of dimensional tables: 1.Slowly changind dimensions(SCD) a)SCD-1:stores only current values b)SCD-2:stores both previous and current values c)SCD-3:stores cu...
The Dimensions are Confirmed Dimension, Junk/Dirty Dimension, Degenerated Dimension and Slowly Changing Dimensions(SCD)-(Under slowly changing dimensions we have 6 types, they are Type1, Type2, Type3, Type4, Type5 and Type6).