The below List of top 20 Data Mart Interview Questions and Answers for freshers and experienced pdf free download
1. What is data mart?
Data Marts is used on a business division/department level. <br>A data mart only contains the required subject specific <br>data for local analysis. <br> A database, or collection of databases, designed to help <br>managers make strategicdecisions about their business. <br>data marts are usually smaller and focus on a particular <br>subject or department. Some data marts, called dependent <br>data marts, are subsets of larger data warehouses. A data <br>mart is a simpler form of a data warehouse focused on a <br>single subject (or functional area) such as sales, finance, <br>marketing, HR etc. Data Mart represents data from single <br>business process.
2. For faster process, what we will do with the Universe?
For a faster process create aggregate tables and write better sql so that the process would fast.
3. What is difference between drill & scope of analysis?
Drilling can be done in drill down, up, through, and across; scope is the overall view of the drill exercise.
4. What is type 2 version dimension?
Version dimension is the SCD type II in real time it using because of it will maintain the current data and full historical data.
5. What is the definitions for Datawarehose and Datamart?
Datamart is subset of Datawarehouse we can say a <br>datamart is collection of individual departmental <br>information...<br>Where as datawarehouse in collection of datamart.
Data mart is a single subject and datawarehouse is a integration of multiple subjects
6. What are Data Marts
Data Mart is a segment of a data warehouse that can provide data for reporting and analysis on a section, unit, department or operation in the company, e.g. sales, payroll, production. Data marts are sometimes complete individual data warehouses which are usually smaller than the corporate data warehouse.
7. Briefly state different between data ware house & data mart?
Data warehouse is made up of many datamarts. DWH contain many subject areas. However, data mart focuses on one subject area generally. E.g. If there will be DHW of bank then there can be one data mart for accounts, one for Loans etc. This is high-level definitions.
8. What is the difference between a data warehouse and a data mart?
A data mart is a subject oriented database which supports the business needs of individual departments within the enterprise.It is an subset of the enterprise data warehouse.It is also known as high performance query structures.
9. What is Meta data?
Metadata is data about data. E.g. if in data mart we are receiving any file. Then metadata will contain information like how many columns, file is fix width/limited, ordering of fields, data types of field etc.
10. what is data validation strategies for data mart validation after loading process
Data validation is generally done manually in DWH in this case if source and TGT are relational you need to create SQL scripts to validate source and target data and if source isFlat file or non relational database you can use excel if data is very less or create dummy tables to validate your ETL code.
11. What is dimension modeling?
A logical design technique that seeks to present the data in a standard, intuitive framework that allows for high-performance access. There are different data modeling concepts like ER Modeling (Entity Relationship modeling), DM (Dimensional modeling), Hierarchal Modeling, Network modeling. However, popular are ER and DM only.
12. Where the cache files stored?
Caches are stored in Repository.
13. How can you import tables from a database?
In Business Objects Universe Designer you can open Table Browser and select the tables needed then insert them to designer.
14. What is drilling across?
Drill across corresponds to switching from 1 classification in 1 dimension to a different classification in different dimension.
15. What is degenerate dimension table?
Degenerate Dimensions: If a table contains the values, which r neither dimension nor measures is called degenerate dimensions. For example invoice id, employee no.A degenerate dimension is data that is dimensional in nature but stored in a fact table.
16. What is an error log table in Informatica occurs and how to maintain it in mapping?
Error Log in Informatica is a one of output file created by Informatica Server while running the session for error messages. It is created in Informatica home directory.
17. What is loop in Data warehousing?
In DWH loops may exist between the tables. If loops exist, then query generation will take more time, because more than one path is available. It creates ambiguity also. Loops can be avoided by creating aliases of the table or by context.
Example: 4 Tables - Customer, Product, Time, Cost forming a close loop. Create alias for the cost to avoid loop.
18. How many clustered indexes can u create for a table in DWH?
In case of truncate and delete command what happens to table, which has unique id.
You can have only one clustered index per table. If you use delete command, you can rollback... it fills your redo log files.
If you do not want records, you may use truncate command, which will be faster and does not fill your redo log file.
19. What is hybrid slowly changing dimension?
Hybrid SCDs are combination of both SCD 1 and SCD 2.It may happen that in a table, some columns are important and we need to track changes for them i.e. capture the historical data for them whereas in some columns even if the data changes, we don't care.For such tables we implement Hybrid SCDs, where in some columns are Type 1 and some are Type 2.You can add that it is not an intelligent key but similar to a sequence number and tied to a time stamp typically!
20. Can a dimension table contain numeric values?
Yes. However, those data type will be char (only the values can numeric/char).Yes, dimensions even contain numerical because these are descriptive elements of our business.
1. What is data mart?
Data Marts is used on a business division/department level. <br>A data mart only contains the required subject specific <br>data for local analysis. <br> A database, or collection of databases, designed to help <br>managers make strategicdecisions about their business. <br>data marts are usually smaller and focus on a particular <br>subject or department. Some data marts, called dependent <br>data marts, are subsets of larger data warehouses. A data <br>mart is a simpler form of a data warehouse focused on a <br>single subject (or functional area) such as sales, finance, <br>marketing, HR etc. Data Mart represents data from single <br>business process.
2. For faster process, what we will do with the Universe?
For a faster process create aggregate tables and write better sql so that the process would fast.
3. What is difference between drill & scope of analysis?
Drilling can be done in drill down, up, through, and across; scope is the overall view of the drill exercise.
4. What is type 2 version dimension?
Version dimension is the SCD type II in real time it using because of it will maintain the current data and full historical data.
5. What is the definitions for Datawarehose and Datamart?
Datamart is subset of Datawarehouse we can say a <br>datamart is collection of individual departmental <br>information...<br>Where as datawarehouse in collection of datamart.
Data mart is a single subject and datawarehouse is a integration of multiple subjects
6. What are Data Marts
Data Mart is a segment of a data warehouse that can provide data for reporting and analysis on a section, unit, department or operation in the company, e.g. sales, payroll, production. Data marts are sometimes complete individual data warehouses which are usually smaller than the corporate data warehouse.
7. Briefly state different between data ware house & data mart?
Data warehouse is made up of many datamarts. DWH contain many subject areas. However, data mart focuses on one subject area generally. E.g. If there will be DHW of bank then there can be one data mart for accounts, one for Loans etc. This is high-level definitions.
8. What is the difference between a data warehouse and a data mart?
A data mart is a subject oriented database which supports the business needs of individual departments within the enterprise.It is an subset of the enterprise data warehouse.It is also known as high performance query structures.
9. What is Meta data?
Metadata is data about data. E.g. if in data mart we are receiving any file. Then metadata will contain information like how many columns, file is fix width/limited, ordering of fields, data types of field etc.
10. what is data validation strategies for data mart validation after loading process
Data validation is generally done manually in DWH in this case if source and TGT are relational you need to create SQL scripts to validate source and target data and if source isFlat file or non relational database you can use excel if data is very less or create dummy tables to validate your ETL code.
11. What is dimension modeling?
A logical design technique that seeks to present the data in a standard, intuitive framework that allows for high-performance access. There are different data modeling concepts like ER Modeling (Entity Relationship modeling), DM (Dimensional modeling), Hierarchal Modeling, Network modeling. However, popular are ER and DM only.
12. Where the cache files stored?
Caches are stored in Repository.
13. How can you import tables from a database?
In Business Objects Universe Designer you can open Table Browser and select the tables needed then insert them to designer.
14. What is drilling across?
Drill across corresponds to switching from 1 classification in 1 dimension to a different classification in different dimension.
15. What is degenerate dimension table?
Degenerate Dimensions: If a table contains the values, which r neither dimension nor measures is called degenerate dimensions. For example invoice id, employee no.A degenerate dimension is data that is dimensional in nature but stored in a fact table.
16. What is an error log table in Informatica occurs and how to maintain it in mapping?
Error Log in Informatica is a one of output file created by Informatica Server while running the session for error messages. It is created in Informatica home directory.
17. What is loop in Data warehousing?
In DWH loops may exist between the tables. If loops exist, then query generation will take more time, because more than one path is available. It creates ambiguity also. Loops can be avoided by creating aliases of the table or by context.
Example: 4 Tables - Customer, Product, Time, Cost forming a close loop. Create alias for the cost to avoid loop.
18. How many clustered indexes can u create for a table in DWH?
In case of truncate and delete command what happens to table, which has unique id.
You can have only one clustered index per table. If you use delete command, you can rollback... it fills your redo log files.
If you do not want records, you may use truncate command, which will be faster and does not fill your redo log file.
19. What is hybrid slowly changing dimension?
Hybrid SCDs are combination of both SCD 1 and SCD 2.It may happen that in a table, some columns are important and we need to track changes for them i.e. capture the historical data for them whereas in some columns even if the data changes, we don't care.For such tables we implement Hybrid SCDs, where in some columns are Type 1 and some are Type 2.You can add that it is not an intelligent key but similar to a sequence number and tied to a time stamp typically!
20. Can a dimension table contain numeric values?
Yes. However, those data type will be char (only the values can numeric/char).Yes, dimensions even contain numerical because these are descriptive elements of our business.
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