Format: 

Data Compiler. Title of Data Set. Title of Website, Publisher, Day Month Year. Dataset. Database Name or Title of Non-Publisher Website, DOI or URL. Accessed Day Month Year.

Data Compiler. Title of Data Set. Title of Website, Publisher, Day Month Year, URL or DOI (when accessed from the publisher's website). Accessed Day Month Year. Dataset.

Data Compiler. Title of Data Set. Title of Website, Publisher, Day Month Year. Database Name or Title of Non-Publisher Website.Dataset.

Examples: 

April 17-May 19, 2013 Online Dating. Pew Research Center, May 2013, pewinternet.org/dataset/may-2013-online-dating/. Accessed 12 Dec. 2017. Dataset.

In-text: (April)

Notes: 

If the data set does not have an identified title, you can provide a generic description in place of the title (e.g. Dataset for online dating); do not italicize the description or wrap it in quotes (MLA 28-29). If the publisher is also the corporate author (as above), omit the author and list the organization in the publisher field only (MLA 25). You can omit the publisher name if it is the same as the website title (MLA 42). Add Dataset at the end of the citation to indicate it is not a standard source (i.e. book or journal article) (MLA 52). You should also provide a DOI (Digital Object Identifier) if available; otherwise, provide the direct URL along with the date of access for the item, but omit the http:// or https:// (MLA 110). Since you will not have page numbers, you can use other numbered labels as appropriate in your in-text citation as above (MLA 56). If the dataset appeared in a published source (e.g. table in a journal article), refer to the dataset in the body of your paper and then site the source as a whole (https://style.mla.org/citing-an-image-in-a-periodical).

Source:

This source type is not covered by the MLA Handbook (8th ed.)