Licensing data
Data Licensing is an important part of sharing your data, as the terms of use when sharing data are subject to what type, if any, of embargo is in place, whether a general license applies to all users, or whether a data sharing agreement must be entered in before access to the data is granted.
Even if you, or your research funder, decide to open or share all your research data, a license is required so that potential re-users know up front what they can do with it and it increases the likelihood that other researchers will consider your data for reuse. Releasing the data without a license creates ambiguity and this is something that you should try to avoid.
Think of the proper license as your official permission for others to use, or own something that you are the copyright owner for (like code you've written, or data you've gathered). Licensing is included in and it is an important part of scholarly communications, guiding others (your colleagues, collaborators, other researchers) to know exactly how they can use your materials, and you can establish boundaries that you are comfortable with.
There is a wide range of licenses you can use, depending on your research data, your research output, the funder's requirements, sensitive data restrictions and more.
Data License Options
Code License Options
There is no single right answer as to which license to assign to a database or content. Remember though, that to apply a license you must own the data. It is imperative to clarify the ownership with your institution and/or your research funder.