system
August 10, 2010, 6:40am
7
What is M---->M cardinality? Is it N:N or 1:N or 0:N?
In short, a fan trap occurs when you have a 1:N cardinality of a join between 2 tables and you have measures in a query from both of the tables (or at least from the table on the “1” end of the 1:N join).
Check more topics about a fan trap:
Hi to everybody…i have 2 simple items in bo universe (2 aggregate indicators) , but when i put them together in a query, Bo think they are incompatible and so the result is this in the picture… he make 2 distinct queryes and then he join…but in pl/sql i usally do only a query, and i have the correct result…what i can do in the designer, to telle that the object are compatible, and that he can do it in only one query? Thanks to everybody!!
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flavio20002 (BOB member since 2010-03-23)
Hi All,
Yes I have searched QUITE a lot on this forum and I think I have covered most of the posts related to this topic. I saw a lot of posts exlaining how to solve them but haven’t come across any that describe the cause of traps. Here are somethings that I need help with:
Fan Trap:
D1 --< F1 --< F2
Fan trap will not exist if the fact tables above are at the same level of granularity no matter where the dimensions/measures are coming from. Is this a fair statement? If yes, then in real wo…
Dear,
I’m suffering a problem in my universe…I freshly created it and it’s based on an RDB model, not a star-scheme unfortunatelly.
I defined some contexts and alias’ed some tables in order to provide clean operation of the universe.
Today I started creating some reports and all went fine untill the measure (yes, ther’s only 1 numeric in the entire report) started multiplying its value from the moment I started adding more tables to the query…
I am designing a universe I am facing a issue where for one record I am fetching 7 records and getting huge values , I should get one record. I have checked the all the joins but could not solve the issue. In my date table I have dates from day,week and month is this some thing to do with it needful advice is helpful
thanks in advance
bobtom (BOB member since 2008-01-17)
I have read the article from Dave on fan traps,A->B->C. Does it mean that if B and C have measures in them then it is a fan trap. Or does it have to be a specific on the type of the measures like for example may be total for orders in B and number of orders in C.
hartford27
If we have three tables and the middle table gets a one to many join on one key from another table ie this table being the many side and its get a one to many join on an other key from an other table again this table being on the many side, what are the common issues.
GC_hill
Hi All,
We are facing a Fan Trap problem. We are having 3 tables which are refered in the report. The relation between these tables is as:
CRT_CURRENCY ----< PRC_RATE-----< CAPACITY_DTL.
The data in these tables is as:
Table CRT_CURRENCY:
CCY_CD LNG_DESC
--------------------------
GBP Pound
USD US Dollar
Table PRC_RATE:
RATE_LINE_ID VER_NO CCY_CD TOT_PROMSD_REV
--------------------------------------------------------------
12345 1 GBP 1000
12345 2…
Marek Chladny (BOB member since 2003-11-27)
(BOB member since 2003-11-27)