61⟩ Tell me what is SCD?
SCD is defined as slowly changing dimensions, and it applies to the cases where record changes over time.
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62⟩ Tell me can we take backup when the database is opened?
No, We cannot take full backup when the database is opened.
63⟩ Tell me why facts table is useful in representing the data?
Fact table allows the measurement and the values of the facts of the data to be contained inside the table. This table consists of the foreign keys and primary keys of the dimension tables. It is located in between the star schema or snowflake schema. It provides values that are additive and independent variables through which the dimensional attributes are analyzed. This table consists of the grains, which consist of atomic level of data and through which the facts in the tables are defined. Each record defines the independent facts that provide higher level of data to be given to the user. It is useful in representing the data due to easy storage and less memory to be taken to the facts of the data that are associated with it.
64⟩ Explain the process that are involved in Data Warehousing?
Data Warehousing involves data cleaning, data integration and data consolidations.
65⟩ Tell me what language is the base of DMQL?
DMQL is based on Structured Query Language (SQL).
66⟩ Explain the types of OLAP server?
There are four types of OLAP servers, namely Relational OLAP, Multidimensional OLAP, Hybrid OLAP, and Specialized SQL Servers.
67⟩ Explain what are the different types of SCD's used in data warehousing?
SCD (Slowly changing dimensions) that provides different attributes that are used for the record that varies over time and doesn't remain stable.
There are three types of SCDs are used in data warehousing. These are defined as:
SCD1: This is the record that is used to replace the original record even there is only one record exists in the database. The current data will be replaced and the new data will take its place.
SCD2: This is the new record file that is added to the dimension table. This record exists in the database with the current data and previous data that is stored in the history.
SCD3: This uses the original data that is modified to the new data. This consists of two record one record that exist in the database and another record that will replace the old database record with the new information.
68⟩ Tell me what is Star Schema?
Star schema is nothing but a type of organizing the tables in such a way that result can be retrieved from the database quickly in the data warehouse environment.
69⟩ Explain me what is surrogate key?
Surrogate key is nothing but a substitute for the natural primary key. It is set to be a unique identifier for each row that can be used for the primary key to a table.
70⟩ Do you know what is the difference between metadata and data dictionary?
Metadata is defined as data about the data. But, Data dictionary contain the information about the project information, graphs, abinito commands and server information.
71⟩ Please explain what is Summary Information?
Summary Information is the area in data warehouse where the predefined aggregations are kept.
72⟩ Tell us which one is faster, Multidimensional OLAP or Relational OLAP?
Multidimensional OLAP is faster than Relational OLAP.
73⟩ Define data warehouse in your own words?
Data warehouse is a subject oriented, integrated, time-variant, and nonvolatile collection of data that supports management's decision-making process.
74⟩ Tell me which language is used for defining Schema Definition?
Data Mining Query Language (DMQL) is used for Schema Definition.
75⟩ Explain me what is Data Mining?
Data Mining is set to be a process of analyzing the data in different dimensions or perspectives and summarizing into a useful information. Can be queried and retrieved the data from database in their own format.
76⟩ Do you know what is Virtual Warehouse?
The view over an operational data warehouse is known as virtual warehouse.
77⟩ Tell me what are the stages that are required in Data warehousing?
There are four different kinds of stages that are required in data warehousing and they are:
Offline Operational Databases: This is the top most and initial stage that allows the database to be viewed offline without going to online. This copy the database to the operational system and an offline server that processes the load of the online and offline and allow the performance to be balanced.
Offline Data Warehouse: This is the second stage where the updation of the time cycle that is regular takes place. The settings are given through which the data can be set like daily, weekly, monthly and yearly. This data is taken from the operational system. The data is stored in the report oriented data structure.
Real Time Data Warehouse: This allows the transaction update on the event basis. It means on an event an updation occurs. The transaction is performed in the operational system as well.
Integrated Data Warehouse: This is the final stage and it is used to generate activity or transactions. After generation they are again put back to the operational system to be used by the user on the daily basis
78⟩ Explain what are the different models used in cluster analysis?
There are many algorithms that can be used to analyze the database to check the maintenance of all the data sets that are already present.
The different types of cluster models include as follows:
☛ Connectivity models:These are the models that connect one cluster to another cluster. This includes the example of hierarchical clustering that is based on the distance connectivity of one model to another model.
☛ Centroid models:These are the models that are used to find the clusters using the single mean vector. It includes the example of k-means algorithm.
☛ Distribution models:It includes the specification of the models that are statistically distributed for example multivariate normal distribution model.
☛ Density models:Deals with the clusters that are densely connected with one another in the regions having the data space.
☛ Group models:Specifies the model that doesn’t provide the refined model for the output and just gives the grouping information.
79⟩ Tell me how many fact tables are there in a star schema?
There is only one fact table in a star Schema.
80⟩ Explain what is the difference between OLTP and OLAP?
OLTP is known as online transaction processing and it refers to the class of systems that manages the transaction oriented applications used for the data entry and processing of the transaction whereas, OLAP stands for online analytical processing that defines an approach to give the reply to multi-dimensional analytical queries. It is a part of business intelligence. It allows the modification to be done of the traditional database terms.
OLTP uses the original data source to be taken in the database. It doesn't create any copy or uses any virtual data. OLAP uses many data sources that are taken from many places and gets stored in the database.
OLTP uses the business process snapshots that will handle the recovery process if any that has to be done in future. Whereas, OLAP uses the snapshots of multi-dimensional views of business activities of planning and decision making that is required to be used in the database.
OLTP uses the normalization database that will slow down the system due the size of the database and the normalization also degrades the performance. Whereas, OLAP uses the de-normalized process and uses the large database so the speed also increases and it improves the overall performance of the system as well
