What is chasm trap in database?
A chasm trap occurs when two “many-to-one” joins converge on a single table, and the query includes measures from both leaf tables. As a result multiple rows are returned from the tables when processing the query.
What is fan trap and chasm trap in DBMS?
The Chasm trap occurs when two “many to one” joins converge on a single table. For example a customer can place many orders/and or place many loans. Fan trap. The Fan trap occurs when a “one to many” join links a table which is in turn linked by another “one to many” join.
Which methods can resolve a chasm trap?
To resolve a chasm trap you need to make two separate queries and then combine the results.
What is connection trap in database?
Connection traps appear when a pathway between two or more entities is either ambiguous or false existent. Relational databases seem like something straightforward, however, correctly written query may not always lead to a correct result.
How do you fix a fan trap in a database?
There are two ways to solve a fan trap problem. Create an alias for the table containing the initial aggregation, then use Detect Contexts (Tools > Detect Contexts) to detect and propose a context for the alias table and a context for the original table. This is the most effective way to solve the fan trap problem.
How do you detect a fan trap in a database?
Fan trap occur in a situation when a model represents relationship between entity types however a path between certain entity occurrences is ambiguous. in this model it may be impossible to determine the branch a staff belongs to, in the situation when staff belong to division having more than 1 branches.
How do you resolve a chasm trap and fan trap?
Resolving a Chasm Trap
- Create a context for each fact table. This solution works in all cases.
- Modify the SQL parameters for the universe so you can generate separate SQL queries for each measure. This solution only works for measure objects. It does not generate separate queries for dimension or detail objects.
What is aggregate awareness in SAP BO?
Aggregate Aware is one of the powerful functions in BO and very common / famous function in Business Objects Designer and reports. It will speeds up the execution of queries, improving the performance of SQL transactions using database Aggregate Tables.
What is the most common design trap and how does it occur?
The most common design trap is known as a fan trap. A fan trap occurs when you have one entity in two 1:M relationships to other entities, thus producing an association among the other entities that is not expressed in the model.
How fan and chasm traps can occur in an ER model?
Fan Trap. It occurs when a model represents a relationship between entity types, but pathway between certain entity occurrences is ambiguous. Chasm Trap. It occurs when a model suggests the existence of a relationship between entity types, but pathway does not exist between certain entity occurrences.
What is derived table in SAP BO?
A Derived Table is a logical table created in Business Objects Universe using an SQL query. A derived table in a universe is analogous to a view created in database with a SELECT statement.
How are fact and dimension tables related in chasm trap?
A chasm trap is simply one specific way that tables in a database schema can be related to one another. To take a step back, in a denormalized data model, you have fact and dimension tables.
How to create a report for chasm trap?
This is common solution for Chasm Trap. Now you can create the report using Measures and their relative dimensions from fact table and each fact table will create separate SQL and data will get synchronized based on common dimension GL Number. Your final report would look like as below with correct result.
When does a chasm trap occur in Sisense?
Chasm Traps. A chasm trap occurs when two “Many-to-One” joins converge on a single table, and the query includes measures from both leaf tables. As a result multiple rows are returned from the tables when processing the query. If you were to calculate both measures (Qty and Value) simultaneously, like in the following example,…
When do many to one joins converge is called chasm trap?
When two “many to one” joins converge on a single table is called Chasm Trap and there should be many to one to Many join relation between 3 three tables. Like the below example, General Ledger (GL) is joined with GL balance Fact and Loan Balance Fact tables in Many ends. Let see how the data looks like in the above tables.