electronic database vs on-line database

electronic database and on-line database both are nouns.

Word	Noun	Adjective	Verb	Adverb
electronic database	Yes	No	No	No
on-line database	Yes	No	No	No

As nouns, electronic database and on-line database are synonyms defined as:

electronic database and on-line database: (computer science) a database that can be accessed by computers

Other synonyms of electronic database include computer database, electronic information service.

electronic database (noun)	on-line database (noun)
(computer science) a database that can be accessed by computers	(computer science) a database that can be accessed by computers