Join functionality - how analytically find the error?


I use a data model that has been working well for a long time. Data records are added at regular intervals (weekly). Now I got in a few components the following error message:

No common parent between table could be found - please check your schema. The Tables [“Table1.DATA”] and [“Table2.DATA”] are connected, but have no common parent table. Join path [Table1]N ← 1![CASES]!1–>N[Table2]. For more information on the join path, search for “Join functionality” in PQL documentation.

I already checked the fields that are linked in the data model.

[Table1.Data].[Field] = MULTIPLE keys
[CASE].[key] = UNIQUE key
[Table2.Data].[Field] = UNIQUE key

I checked this with the following code:

SELECT “Field”, COUNT(“Field”) AS Anzahl FROM “Table2” GROUP BY “Field” HAVING (COUNT(“Field”)>1);

Does anyone have an idea how the analysis of the error can be advanced here? Is it really only due to one of the tables described in the error or is it possibly due to a different table in the data model? Why is the table described with an “N” in the error message, even though the content of the connected field is unique?

many thx

Hi Stefan,

My guess is that you have a 1:1 relationship between CASES and Table2. However, in the PQL engine, all connections are 1:N. In case of a 1:1 relationship, the direction which is specified in the data model is taken. Can you check how you configured the direction in the data model? To do this, go to the data model, click on the foreign key edge between the two tables, and make sure that the CASES table is on the right, defined as the Parent/N table. If that is not the case, please swap the tables, and reload the data model.


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Dear David,

perfect - your tip was successful.