Databases use controlled keywords (known as thesaurus or subject terms) to categorize each record stored. The subject headings vary for each database according to their indexing system. Using the term "qualitative research" in Sociological Abstracts will yield results that include qualitative methods (but may not be limited to qualitative methods).
This strategy uses text or keywords that might specifically identify qualitative research and searches the titles, abstracts and keywords of records held in the databases. Some Text Words include: qualitative, ethnograph*, phenomenol*, ethnonurs*, grounded theor*, purposive sample, hermeneutic*, heuristic*, semiotics, lived experience*, narrative*, life experiences, cluster sample, action research, observational method, content analysis, thematic analysis, constant comparative method, field stud*, theoretical sample, discourse analysis, focus group*, ethnological research, ethnomethodolog*, interview*.
More keywords to consider:

Qualitative Research Filters are pre-formulated search strategies that have been constructed by librarians to help you retrieve articles in databases that deal with qualitative research. You can use the filter and then combine the results with your subject.
Adapted from The University of Washington's Finding Qualitative Sources Guide