BDC Association Error

I was doing association between 2 entities using business data catalog (BDC) in SharePoint but while importing meta-date file I was getting the following error:

Application definition import failed. The following error occurred: The IdentifierName Attribute of the TypeDescriptor named 'columnName' of the Parameter named 'returnParameter' of the Method named 'methodName' of the Entity named 'entityName' does not match any of the defined Identifiers for the Entity. Error was encountered at or just before Line: '157' and Position: '24'.

Another error which I was getting on the page sometimes as follow:

The Business Data Catalog is configured incorrectly. Administrators, see the server log for more information.

That error is found within the Servers Event Log:

A Metadata Exception was constructed in App Domain '/LM/W3SVC/1959965621/Root-2-128667808042048704'. The full exception text is: Could not find appropriate places on the root TypeDescriptor to read sub-identifier values for the Instance of Entity 'entityName'.

After digging into the error I found that while doing the association between 2 entities, identifier which is used in order to call the method in one entity, same identifier should also be present in other entity, otherwise association will never be successful and user will keep on facing aforementioned errors.

Note:- While performing the association between two entities, database schema should support the BDC association model and all the identifiers should be defined properly in all entities.

I am hoping that this will save time of someone in future.