Why do Fan traps happen?
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.
What is fan trap in ER diagram?
Answer. Fan Trap: A (master) table linking to multiple tables in a one-to-many relationship. An example in different notation, so that you can understand it in your preferred notation. This becomes problematic when you want to run some query like to get the department for a particular employee.
What is a fan trap problem how we solve this problem?
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.
Why is it called a chasm trap?
A chasm trap occurs when two many-to-one joins converge on a single table. In a complex schema, you may have a fact table with no relationship to another fact table, except that each contains a foreign key to a shared dimension table. This is known as a chasm trap, and ThoughtSpot can handle it!
What is difference between fan trap and chasm trap?
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. The Fan trap occurs when a “one to many” join links a table which is in turn linked by another “one to many” join.
How do you stop a fan trap?
How do you get rid of chasm traps?
If you have two fact tables with many to one joins converging to a single lookup table, then you have a potential chasm trap. To resolve a chasm trap you need to make two separate queries and then combine the results.
What is a chasm trap?
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.
How do you stop a chasm trap?
A quick SQL solution to ‘Chasm Trap’ is a pre-aggregated join of the tables like this: Or an alternative solution can be to study again the data model and look at superfluous or wrongly assumed data relationships and dependencies. Maybe the dimension table is not meant to be shared.
What are the problems with E-R model?
The E-R model can result problems due to limitations in the way the entities are related in the relational databases. These problems are called connection traps. These problems often occur due to a misinterpretation of the meaning of certain relationships.
What trap can be eliminated by reconstructing the E-R model?
The fan trap is resolved by restructuring the original ER model to represent the correct association.