to check the attribute exist and assign the value

[Jasmine]

If attr.error exist then Error will be attr.error. If attr.error not exist and attr.error.errmsg exist then Error would be attr.error.errmsg.  i have tried the below code. only one case works other case fails. please advise

eval Error=case(NOT attr.error =="*", 'attr.error',NOT attr.error.errmsg =="*", 'attr.error.errmsg')

[bowesmana]

What @richgalloway said, but whenever you reference a JSON field containing dots in the right hand side of an eval you MUST wrap the field name in single quotes, i.e. the first suggestion should be

eval Error=case(isnotnull('attr.error'), 'attr.error', 
                isnotnull('attr.error.errmsg'), 'attr.error.errmsg')

but for your solution the coalesce() option would make sense - note there the use of single quotes - always for the right hand side of the eval. 

This applies not just to JSON field names, but any field name that contains non simple characters or field names that start with numbers.

[richgalloway]

Check for the existence of a field with the isnotnull() function.

eval Error=case(isnotnull(attr.error), 'attr.error', isnotnull(attr.error.errmsg), 'attr.error.errmsg')

or use the coalesce() function, which does the tests for you and selects the first listed field that is not null.

eval Error=coalesce('attr.error','attr.error.errmsg')