Q. If you are using a database do you have to include the URL when citing an article in MLA format?

The following information is from the Writing Center MLA Handout 

DOI and URL: The digital object identifier (DOI) is a set of characters that is assigned to a specific online document to make it easier to find. The DOI is similar to a URL, but more reliable, because the DOI is assigned only to that particular original source. Unlike URLs, it never changes. • If a publisher specifies a DOI, include it in the citation entry instead of the URL • If the DOI is not preceded by http:// or https://, precede it with https://doi.org Example: https://doi.org:10.1177/0269881118806297 Note: DOIs and URLs can be complex. Shortened versions of either is acceptable. • To create unique, short DOIs, go to: http://shortdoi.org/ • If using a shortened-URL service, make sure the link goes to the proper location.