The general format for citing data using the APA 6th ed. (p. 211) is as follows (the title of a data set should be italized):
Rightsholder, A. A. (Year). Title of program (Version number) [Description of form]. Location: Name of producer.
Rightsholder, A. A. (Year). Title of program [Description of form]. Retrieved from http://xxx
if you have a Digital Object Identifier (doi), you can use it in place of the URL.
The form descriptions can vary, examples include the following:
Bureau of Labor Statistics. (2016). Consumer price index - all urban consumers, 1956-2016 [Time series]. Retrieved from http://data.bls.gov
Pew Research Center. (2016). June 10-July 12, 2015 – Gaming, Jobs and Broadband [Data file and code book]. Retrieved from http://www.pewresearch.org
U.S. Department of Health and Human Services, Substance Abuse and Mental Health Services Administration, Office of Applied Studies. (2013). Treatment episode data set -- discharges (TEDS-D) -- concatenated, 2006 to 2009 [Data set]. doi:10.3886/ICPSR30122.v2
World Bank, World Development Indicators. (2016). Firms using banks to finance working capital (% of firms) [Data file]. Retrieved from http://data.worldbank.org/indicator/IC.FRM.BKWC.ZS?view=chart
The third item cited above was retrieved from the APA Blog at http://blog.apastyle.org/apastyle/2013/12/how-to-cite-a-data-set-in-apa-style.html
APA doesn't specifiy a format for those data sets that might be dynamic. But you could include when the data was generated in place of a URL. Ask your instructor what he/she prefers. See example below:
Bureau of Labor Statistics. (2016). Consumer price index - all urban consumers, 1956-2016 [Time series]. Generated July 6, 2016 (11:37:53 AM)
There are a number of LibGuides/Research Guides and FAQs on the Internet with examples for citing. Here are a few of them.