Cannot create relationship: Error:Missing index on column(s) I am trying to make relation on 2 tables in database designer.

I am using relationship tool. Below are the steps followed: 


I clicked on the ID in table lekar.
Then I click on lekar column in the next table.
Pressed OK.


It throws the below error, what is the problem ? 

Error: Missing index on column(s).


I added ID column so it will have indexing, but it still does not work.
Ahoj Hynku,

zkus tam přidat CONSTRAINT id nebo/a FOREIGN KEYids referencí na druhou tabulku s 'Id' sloupcem.

Hi Hynek,

You can try add CONSTRAINT id or/and FOREIGN KEYid with refernece on second table with 'Id' column.