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    which relationship we cannot perform in cognos one to one many to many many to one one to many

    Mohammed

    Guys, does anyone know the answer?

    get which relationship we cannot perform in cognos one to one many to many many to one one to many from screen.

    Relationships

    A relationship describes how to create a relational query for multiple objects in the model. Without relationships, these objects are isolated sets of data.

    Relationships

    A relationship describes how to create a relational query for multiple objects in the model. Without relationships, these objects are isolated sets of data.

    Relationships work in both directions. You often must examine both directions to fully understand the relationship.

    The different types of relationships are

    one-to-one

    One-to-one relationships occur when one instance of data in a query subject relates to exactly one instance of another. For example, each student has one student number.

    one-to-many or zero-to-many

    One-to-many or zero-to-many relationships occur when one instance of data in a query subject relates to many instances of another. For example, each teacher has many students.

    many-to-many

    Many-to-many relationships occur when many instances of data in a query subject relate to many instances of another. For example, many students have many teachers.

    When importing metadata, Framework Manager can create relationships between objects in the model based on the primary and foreign keys in the data source. You can create or remove relationships in the model so that the model better represents the logical structure of your business.

    After you import metadata, verify that the relationships you require exist in the project and that the cardinality is set correctly. The data source may have been designed without using referential integrity. Often, many primary and unique key constraints are not specified. Without these constraints, Framework Manager cannot generate the necessary relationships between fact tables and dimension tables.

    Framework Manager stores relationships in the nearest common parent of the objects that participate in the relationship. The parent can be either a folder or a namespace. If you move one of the participating objects outside the common parent, the relationship moves to the next namespace that is common to both ends of the relationship. If you move a relationship to a different folder or namespace, the participating objects also move to the same folder or namespace.

    Tip: Use the Search tab (Tools pane) to find an object of class Relationship whose name matches a specified pattern. For example, if you search for a relationship whose name contains Order Header, Framework Manager finds all relationships that have Order Header as one end. If you renamed a relationship, a search of this type may not find it.

    Cardinality

    Relationships exist between two query subjects. The cardinality of a relationship is the number of related rows for each of the two query subjects. The rows are related by the expression of the relationship; this expression usually refers to the primary and foreign keys of the underlying tables.

    IBM Cognos 8 uses the cardinality of a relationship in the following ways:

    to avoid double-counting fact data

    to support loop joins that are common in star schema models

    to optimize access to the underlying data source system

    to identify query subjects that behave as facts or dimensions

    A query that uses multiple facts from different underlying tables is split into separate queries for each underlying fact table. Each single fact query refers to its respective fact table as well as to the dimensional tables related to that fact table. Another query is used to merge these individual queries into one result set. This latter operation is generally referred to as a stitched query. You know that you have a stitched query when you see coalesce and a full outer join.

    A stitched query also allows IBM Cognos 8 to properly relate data at different levels of granularity .

    You must ensure that all relationships and cardinality correctly reflect your users’ reporting requirements.

    For more information, see Cardinality in Generated Queries and Cardinality in the Context of a Query.

    Detecting Cardinality from the Data Source

    When importing from a relational data source, cardinality is detected based on a set of rules that you specify. The available options are

    use primary and foreign keys

    use matching query item names that represent uniquely indexed columns

    use matching query item names

    The most common situation is to use primary and foreign keys as well as matching query items that represent uniquely indexed columns. The information is used to set some properties of query items as well as to generate relationships.

    To view the index and key information that was imported, right-click a query subject and click Edit Definition. For a query subject, you can change the information in the Determinants tab.

    Optional relationships, full outer joins, and many-to-many relationships can be imported from your data source. Framework Manager will run them as queries.

    Note: All regular dimensions begin as query subjects. If you converted a query subject to a regular dimension, note that determinant information for the query subject is leveraged as a starting point to define the levels of a single hierarchy. We recommend that you review the levels and keys created in the hierarchy of the dimension.

    Notation

    By default, Framework Manager uses Merise notation. Merise notation marks each end of the relationship with the minimum and maximum cardinality of that end. You can also use Crowsfeet notation, which provides a pictorial representation of the relationship. For information about how to change the notation, see Change the Settings for Diagrams.

    स्रोत : bsc.ipportalegre.pt

    Relationships

    A relationship describes how to create a relational query for multiple objects in the model. Without relationships, these objects are isolated sets of data.

    Relationships

    Last Updated: 2022-08-10

    A relationship describes how to create a relational query for multiple objects in the model. Without relationships, these objects are isolated sets of data.

    Relationships work in both directions. You often must examine both directions to fully understand the relationship.

    The different types of relationships are

    One-to-one

    One-to-one relationships occur when one instance of data in a query subject relates to exactly one instance of another. For example, each student has one student number.

    One-to-many or zero-to-many

    One-to-many or zero-to-many relationships occur when one instance of data in a query subject relates to many instances of another. For example, each teacher has many students.

    Many-to-many

    Many-to-many relationships occur when many instances of data in a query subject relate to many instances of another. For example, many students have many teachers.

    When importing metadata, IBM® Cognos® Framework Manager can create relationships between objects in the model based on the primary and foreign keys in the data source. You can create or remove relationships in the model so that the model better represents the logical structure of your business.

    After you import metadata, verify that the relationships you require exist in the project and that the cardinality is set correctly. The data source may have been designed without using referential integrity. Often, many primary and unique key constraints are not specified. Without these constraints, Framework Manager cannot generate the necessary relationships between fact tables and dimension tables.

    Framework Manager stores relationships in the nearest common parent of the objects that participate in the relationship. The parent can be either a folder or a namespace. If you move one of the participating objects outside the common parent, the relationship moves to the next namespace that is common to both ends of the relationship. If you move a relationship to a different folder or namespace, the participating objects also move to the same folder or namespace.

    Tip: Use the Search tab (Tools pane) to find an object of class Relationship whose name matches a specified pattern. For example, if you search for a relationship whose name contains Order Header, Framework Manager finds all relationships that have Order Header as one end. If you renamed a relationship, a search of this type may not find it.

    स्रोत : www.ibm.com

    Cognos

    Cognos - Relationships in Metadata Model, Relationships are used to create queries on multiple objects in a metadata model. Relationships can be bidirectional and without creating relationship, objects

    Cognos - Relationships in Metadata Model

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    Relationships are used to create queries on multiple objects in a metadata model. Relationships can be bidirectional and without creating relationship, objects are individual entities with no use in metadata model.

    Each object in metadata model is connected using primary or foreign key in the data source. You can create or remove relationships in the metadata model to meet the business requirements.

    There are different relationships which are possible, some of them are −

    One to One − When an instance of one query subject is related to another instance. For example: Each customer has one customer id.One to Many − This relationship occurs when one instance of query subject relates to multiple instances. For example: Each doctor has many patients.Many to Many − This relationship occurs when many instances of a query subject relates to multiple instances. For example: Each patient has many doctors.

    Cardinality Concept

    It is defined as the number of related rows for each of the two query subjects. Cardinality is used in the following ways −

    Loop Joins in Star schema

    Optimized access to data source

    Avoid double counting fact data

    While using the Relational database as a data source, Cardinality can be defined considering the following rules −

    Primary and Foreign keys

    Match query item names represent uniquely indexed columns

    Matching query item names

    The most common ways to define Cardinality is by using the primary and foreign key. To view the key information that was imported, right click on the query subject → Edit Definition. You can import many to many relationships, optional relationships, and outer joins from the data source.

    Relationship Notation in Metadata Model

    In the Framework manager, a relation is represented by Merise notation. The first part of this notation represents the type of join for this relationship.

    0..1 represents zero or one match

    1..1 represents one to one match

    0..n represents Zero or no matches

    1..n represents One or more matches

    1 − An inner join with all matching rows from both objects.

    0 − An Outer join with all objects from both, including the items that don’t match.

    Creating or Modifying the Relationships

    To create a Relationship or to combine logically related objects which are not joined in metadata import. You can manually create relationship between objects or can automatically define relationship between objects based on selected criteria.

    To create a Relationship, use CTRL key to select one or more query items, subjects or dimensions. Then go to Action Menu → Create Relationship.

    If this is a valid Relationship, the Framework manager wants to create a shortcut to the relationship. You can then click on the OK button.

    Once you create a relationship after the metadata import, you can also modify the relationship or Cardinality in the Framework manager.

    To edit a Relationship, click a relationship and from Action menu → click Edit Definition.

    From the Relationship Expression tab → Select Query items, Cardinalities and Operators.

    To create an additional Join, go to the Relationship Expression tab → New Link and Define New Relationship.

    To test this Relationship, go to Relationship SQL tab → rows to be returned → Test.

    Click on OK button.

    Creating a Relationship Shortcut

    A Relationship shortcut is defined as the pointer to an existing relationship and to reuse the definition of an existing relationship. When you make any change to the source Relationship, they are automatically updated in shortcuts. Relationship shortcuts are also used to resolve ambiguous relationship between query subjects.

    The Framework Manager asks whether you want to create a relationship shortcut whenever you create a relationship and both these conditions are true.

    At least one end for the new relationship is a shortcut.

    A relationship exists between the original objects.

    Go to Action Menu → Create Relationship.

    If this is a valid Relationship, Framework manager wants to create a shortcut to the relationship. Click YES. A list appears of all relationships in which one end is a model object and the other end is either another model object or a shortcut to another model object.

    Click OK.

    Create a Query Subject

    A query subject is defined as a set of query items that have an inherent relationship. A query subject can be used to customize the data they retrieve using a Framework Manager.

    The following are the query subject types in a Framework Manager −

    Data Source Query Subject − These are based on the Relational metadata defined by the SQL statements and are automatically created for each table and view when you import metadata into model.Model Query Subjects − They are not directly created from a data source but are based on the query items defined in other query subjects or dimensions. Using the model query subject, it allows you to create more abstract and business view of data source.

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