Cardinality Check

building semantic layer
1

Hi,

I checked cardinalities for list of tables avail in Universe structure. Everything goes OK except cardinality: Error: “Tabl1.Col1=Tab2.Col1” Unknown cardinality. By hitting Detect button also getting same error.

Please help me out…

Thanks

BOCP (BOB member since 2007-07-02)

2

Well, do you have two tables with those names and a join between them?

Nick Daniels :uk: (BOB member since 2002-08-15)

3

Yes Nick… I have.

What i should do now?? Please

Thanks

BOCP (BOB member since 2007-07-02)

4

Look at the Cardinality of the join!!!

Nick Daniels :uk: (BOB member since 2002-08-15)

5

Please read one of the many MANY posts in this forum that suggest that automatic cardinality detection is worthless. You should set the cardinality manually based on your knowledge of the database.

Dave Rathbun :us: (BOB member since 2002-06-06)

6

@ Nick: It showing “Unknown Cardinality(UNV XXXXXX)” after hitting DETECT button.

@ Dave: Yes, you’re right and i saw many posts also.
Based on DB knowledge i joined but when doing Check Integrity it showing : 4 Divergies with Unknown Cardinality(UNV XXXXXX).

Am in right direction or not?? Please help me…

Thanks

BOCP (BOB member since 2007-07-02)

7

It’s not worthless.

I once used it identify an error in my ETL, and the error I was getting was unknown cardinality.

Damocles :uk: (BOB member since 2006-10-05)

8

@BOCP: You set the join, but did you set the cardinality too?

@Damocles: I would hardly rely on the cardinality detection algorithm to detect issues with my ETL. I would have expected it to be far more reliable (and obvious) that you would detect issues on the reports. Just my opinion, of course. :slight_smile:

Dave Rathbun :us: (BOB member since 2002-06-06)

9

I didn’t rely on it, and I don’t, it was a tool that helped identify the issue.

Damocles :uk: (BOB member since 2006-10-05)

10

Yes Dave. I did that also.

Still it showing divergies : Unknown Cardinality(DXX 000XXX).

Is it behaving because of database tables structure or what?? As i have unnormalised DB(SQL Server) means, without PK, FK…

Thanks

BOCP (BOB member since 2007-07-02)

11

When the data is “wrong” or there are other issues then you will never be able to fix that error. There’s a reason why the “Check Cardinality” option is outside of the box for the “Check All” options.

Dave Rathbun :us: (BOB member since 2002-06-06)