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Given the following schema:

  • Staff (sid, sname)
  • Project (pid, pdesc, pfrom, pto)
  • Asset (aid, acat, adesc)
  • Workfor (sid, pid, wfrom, wto)
  • Assignment (aid, sid, pid, afrom, ato)

Note: The bold attributes are the keys.

Find the names of the staffs who worked or are working for more than one project, in Tuple Relational Calculus.

I was thinking of using count() but it is not allowed in TRC (or according to my Prof). Any answers appreciated.

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    "working for more than one project" = "working for two projects (or more)" = "working for two different projects". Does that help? – ypercubeᵀᴹ May 2 '18 at 10:06

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