What Is Star, Snowflake And Star Flake Schema?
Star schema: In star schema fact table will be directly linked with all dimension tables. The star schema’s dimensions are denormalized with each dimension being represented by a single table. In a star schema a central fact table connects a number of individual dimension tables.
Snowflake: The snowflake schema is an extension of the star schema, where each point of the star explodes into more points. In a star schema, each dimension is represented by a single dimensional table, whereas in a snowflake schema, that dimensional table is normalized into multiple lookup tables, each representing a level in the dimensional hierarchy. In snow flake schema fact table will be linked directly as well as there will be some intermediate dimension tables between fact and dimension tables.
Star flake: A hybrid structure that contains a mixture of star(denormalized) and snowflake(normalized) schema’s.
How Will You Hide An Attribute?
We can hide the attribute by selecting “AttributeHierarchyVisible = False” in properties of the attribute.
How Will You Make An Attribute Not Process?
By selecting “ AttributeHierarchyEnabled = False”, we can make an attribute not in process.
What Is Use Of Isaggregatable Property?
In Analysis Service we generally see all dimension has All member. This is because of IsAggregatable property of the attribute. You can set its value to false, so that it will not show All member. Its default member for that attribute. If you hide this member than you will have to set other attribute value to default member else it will pick some value as default and this will create confusion in browsing data if someone is not known to change in default member.
What Are Key, Name And Value Columns Of An Attribute?
Key column of any attribute: Contains the column or columns that represent the key for the attribute, which is the column in the underlying relational table in the data source view to which the attribute is bound. The value of this column for each member is displayed to users unless a value is specified for the NameColumn property.
Name column of an attribute: Identifies the column that provides the name of the attribute that is displayed to users, instead of the value in the key column for the attribute. This column is used when the key column value for an attribute member is cryptic or not otherwise useful to the user, or when the key column is based on a composite key. The NameColumn property is not used in parent-child hierarchies; instead, the NameColumn property for child members is used as the member names in a parent-child hierarchy.
Value columns of an attribute: Identifies the column that provides the value of the attribute. If the NameColumn element of the attribute is specified, the same DataItem values are used as default values for the ValueColumn element. If the NameColumn element of the attribute is not specified and the KeyColumns collection of the attribute contains a single KeyColumn element representing a key column with a string data type, the same DataItem values are used as default values for the ValueColumn element.
What Are The Difficulties Faced In Cube Development?
Giving attribute relationships
Calculations
Giving dimension usage (many to many relationship)
Analyzing the requirements
What Is Impersonation? What Are The Different Impersonation Options Available In Ssas?
Impersonation allows SSAS to assume the identity/security context of the client application which is used by SSAS to perform the server side data operations like data access, processing etc. As part of impersonation, the following options are available in SSAS
Use a specific Windows user name and password: This option lets you to specify Windows account credentials which will be used by SSAS to perform operations like source data access, processing etc.
Use the service account: When this option is selected, SSAS uses the credentials of the service account under which the Analysis Services service is configured/running for source data access, processing etc.
Use the credentials of the current user: When this option is set, SSAS uses the credentials of the current user for performing operations like DMX Open Queries, Local cubes etc. This option cannot be used for performing server side operations like source data access, processing etc.
Inherit: This option let's the SSAS server decide which impersonation mode is suitable for each type of operation. When this option is set, by default SSAS will use the service account for operations like processing and the credentials of the current user for operations like Local cubes, querying the data mining models, etc...
What Is A Data Source? What Are The Different Data Sources Supported By Ssas?
A Data Source contains the connection information used by SSAS to connect to the underlying database to load the data into SSAS during processing. A Data Source primarily contains the following information (apart from various other properties like Query timeout, Isolation etc.)
Provider
Server Name
Database Name
Impersonation Information
• SSAS Supports both .Net and OLE DB Providers. Following are some of the major sources supported by SSAS: SQL Server, MS Access, Oracle, Teradata, IBM DB2, and other relational databases with the appropriate OLE DB provider.
What Is Sql Server Analysis Services (ssas)?
SQL Server Analysis Services (SSAS) is the On-Line Analytical Processing (OLAP) Component of SQL Server. SSAS allows you to build multidimensional structures called Cubes to pre-calculate and store complex aggregations, and also to build mining models to perform data analysis to identify valuable information like trends, patterns, relationships etc. within the data using Data Mining capabilities of SSAS, which otherwise could be really difficult to determine without Data Mining capabilities.
SSAS comes bundled with SQL Server and you get to choose whether or not to install this component as part of the SQL Server Installation.
What Is Attribute Hierarchy?
An attribute hierarchy is created for every attribute in a dimension, and each hierarchy is available for dimensioning fact data. This hierarchy consists of an “All” level and a detail level containing all members of the hierarchy.
you can organize attributes into user-defined hierarchies to provide navigation paths in a cube. Under certain circumstances, you may want to disable or hide some attributes and their hierarchies.
What Is Use Of Attributehierarchydisplayfolder Property ?
AttributeHierarchyDisplayFolder: Identifies the folder in which to display the associated attribute hierarchy to end users. For example if I set the property value as “Test” to all the Attributes of a dimension then a folder with the name “Test” will be created and all the Attributes will be placed into the same.
What Is Use Of Attributehierarchyenabled?
AttributeHierarchyEnabled: Determines whether an attribute hierarchy is generated by Analysis Services for the attribute. If the attribute hierarchy is not enabled, the attribute cannot be used in a user-defined hierarchy and the attribute hierarchy cannot be referenced in Multidimensional Expressions (MDX) statements.
What Is Use Of Attribute Hierarchy Optimized State?
Attribute Hierarchy Optimized State
Determines the level of optimization applied to the attribute hierarchy. By default, an attribute hierarchy is FullyOptimized, which means that Analysis Services builds indexes for the attribute hierarchy to improve query performance. The other option, NotOptimized, means that no indexes are built for the attribute hierarchy. Using NotOptimized is useful if the attribute hierarchy is used for purposes other than querying, because no additional indexes are built for the attribute. Other uses for an attribute hierarchy can be helping to order another attribute.
What Is Use Of Attribute Hierarchy Ordered ?
Attribute Hierarchy Ordered: Determines whether the associated attribute hierarchy is ordered. The default value is True. However, if an attribute hierarchy will not be used for querying, you can save processing time by changing the value of this property to False.
What Is The Use Of Attributehierarchyvisible ?
AttributeHierarchyVisible : Determines whether the attribute hierarchy is visible to client applications. The default value is True. However, if an attribute hierarchy will not be used for querying, you can save processing time by changing the value of this property to False.
What Are Types Of Storage Modes?
There are three standard storage modes in OLAP applications
MOLAP
ROLAP
Star schema: In star schema fact table will be directly linked with all dimension tables. The star schema’s dimensions are denormalized with each dimension being represented by a single table. In a star schema a central fact table connects a number of individual dimension tables.
Snowflake: The snowflake schema is an extension of the star schema, where each point of the star explodes into more points. In a star schema, each dimension is represented by a single dimensional table, whereas in a snowflake schema, that dimensional table is normalized into multiple lookup tables, each representing a level in the dimensional hierarchy. In snow flake schema fact table will be linked directly as well as there will be some intermediate dimension tables between fact and dimension tables.
Star flake: A hybrid structure that contains a mixture of star(denormalized) and snowflake(normalized) schema’s.
How Will You Hide An Attribute?
We can hide the attribute by selecting “AttributeHierarchyVisible = False” in properties of the attribute.
How Will You Make An Attribute Not Process?
By selecting “ AttributeHierarchyEnabled = False”, we can make an attribute not in process.
What Is Use Of Isaggregatable Property?
In Analysis Service we generally see all dimension has All member. This is because of IsAggregatable property of the attribute. You can set its value to false, so that it will not show All member. Its default member for that attribute. If you hide this member than you will have to set other attribute value to default member else it will pick some value as default and this will create confusion in browsing data if someone is not known to change in default member.
What Are Key, Name And Value Columns Of An Attribute?
Key column of any attribute: Contains the column or columns that represent the key for the attribute, which is the column in the underlying relational table in the data source view to which the attribute is bound. The value of this column for each member is displayed to users unless a value is specified for the NameColumn property.
Name column of an attribute: Identifies the column that provides the name of the attribute that is displayed to users, instead of the value in the key column for the attribute. This column is used when the key column value for an attribute member is cryptic or not otherwise useful to the user, or when the key column is based on a composite key. The NameColumn property is not used in parent-child hierarchies; instead, the NameColumn property for child members is used as the member names in a parent-child hierarchy.
Value columns of an attribute: Identifies the column that provides the value of the attribute. If the NameColumn element of the attribute is specified, the same DataItem values are used as default values for the ValueColumn element. If the NameColumn element of the attribute is not specified and the KeyColumns collection of the attribute contains a single KeyColumn element representing a key column with a string data type, the same DataItem values are used as default values for the ValueColumn element.
What Are The Difficulties Faced In Cube Development?
Giving attribute relationships
Calculations
Giving dimension usage (many to many relationship)
Analyzing the requirements
What Is Impersonation? What Are The Different Impersonation Options Available In Ssas?
Impersonation allows SSAS to assume the identity/security context of the client application which is used by SSAS to perform the server side data operations like data access, processing etc. As part of impersonation, the following options are available in SSAS
Use a specific Windows user name and password: This option lets you to specify Windows account credentials which will be used by SSAS to perform operations like source data access, processing etc.
Use the service account: When this option is selected, SSAS uses the credentials of the service account under which the Analysis Services service is configured/running for source data access, processing etc.
Use the credentials of the current user: When this option is set, SSAS uses the credentials of the current user for performing operations like DMX Open Queries, Local cubes etc. This option cannot be used for performing server side operations like source data access, processing etc.
Inherit: This option let's the SSAS server decide which impersonation mode is suitable for each type of operation. When this option is set, by default SSAS will use the service account for operations like processing and the credentials of the current user for operations like Local cubes, querying the data mining models, etc...
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| PricewaterhouseCoopers Most Frequently Asked Latest SSAS Interview Questions Answers |
What Is A Data Source? What Are The Different Data Sources Supported By Ssas?
A Data Source contains the connection information used by SSAS to connect to the underlying database to load the data into SSAS during processing. A Data Source primarily contains the following information (apart from various other properties like Query timeout, Isolation etc.)
Provider
Server Name
Database Name
Impersonation Information
• SSAS Supports both .Net and OLE DB Providers. Following are some of the major sources supported by SSAS: SQL Server, MS Access, Oracle, Teradata, IBM DB2, and other relational databases with the appropriate OLE DB provider.
What Is Sql Server Analysis Services (ssas)?
SQL Server Analysis Services (SSAS) is the On-Line Analytical Processing (OLAP) Component of SQL Server. SSAS allows you to build multidimensional structures called Cubes to pre-calculate and store complex aggregations, and also to build mining models to perform data analysis to identify valuable information like trends, patterns, relationships etc. within the data using Data Mining capabilities of SSAS, which otherwise could be really difficult to determine without Data Mining capabilities.
SSAS comes bundled with SQL Server and you get to choose whether or not to install this component as part of the SQL Server Installation.
What Is Attribute Hierarchy?
An attribute hierarchy is created for every attribute in a dimension, and each hierarchy is available for dimensioning fact data. This hierarchy consists of an “All” level and a detail level containing all members of the hierarchy.
you can organize attributes into user-defined hierarchies to provide navigation paths in a cube. Under certain circumstances, you may want to disable or hide some attributes and their hierarchies.
What Is Use Of Attributehierarchydisplayfolder Property ?
AttributeHierarchyDisplayFolder: Identifies the folder in which to display the associated attribute hierarchy to end users. For example if I set the property value as “Test” to all the Attributes of a dimension then a folder with the name “Test” will be created and all the Attributes will be placed into the same.
What Is Use Of Attributehierarchyenabled?
AttributeHierarchyEnabled: Determines whether an attribute hierarchy is generated by Analysis Services for the attribute. If the attribute hierarchy is not enabled, the attribute cannot be used in a user-defined hierarchy and the attribute hierarchy cannot be referenced in Multidimensional Expressions (MDX) statements.
What Is Use Of Attribute Hierarchy Optimized State?
Attribute Hierarchy Optimized State
Determines the level of optimization applied to the attribute hierarchy. By default, an attribute hierarchy is FullyOptimized, which means that Analysis Services builds indexes for the attribute hierarchy to improve query performance. The other option, NotOptimized, means that no indexes are built for the attribute hierarchy. Using NotOptimized is useful if the attribute hierarchy is used for purposes other than querying, because no additional indexes are built for the attribute. Other uses for an attribute hierarchy can be helping to order another attribute.
What Is Use Of Attribute Hierarchy Ordered ?
Attribute Hierarchy Ordered: Determines whether the associated attribute hierarchy is ordered. The default value is True. However, if an attribute hierarchy will not be used for querying, you can save processing time by changing the value of this property to False.
What Is The Use Of Attributehierarchyvisible ?
AttributeHierarchyVisible : Determines whether the attribute hierarchy is visible to client applications. The default value is True. However, if an attribute hierarchy will not be used for querying, you can save processing time by changing the value of this property to False.
What Are Types Of Storage Modes?
There are three standard storage modes in OLAP applications
MOLAP
ROLAP
HOLAP.
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