  We describe the WFCAM Science Archive (WSA), which is the primary point of
access for users of data from the wide-field infrared camera WFCAM on the
United Kingdom Infrared Telescope (UKIRT), especially science catalogue
products from the UKIRT Infrared Deep Sky Survey (UKIDSS). We describe the
database design with emphasis on those aspects of the system that enable users
to fully exploit the survey datasets in a variety of different ways. We give
details of the database-driven curation applications that take data from the
standard nightly pipeline-processed and calibrated files for the production of
science-ready survey datasets. We describe the fundamentals of querying
relational databases with a set of astronomy usage examples, and illustrate the
results.
