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我有這些表關係代數具體操作
Employee(ssn, name, sex, address, salary, bdate, dno, superssn)
fk:superssn is ssn in Employee
fk:dno is dnumber in Department
Department(dnumber, dname, mgrssn, mgrstartdate)
fk:mgrssn is ssn in Employee
Dept_locations(dnumber, dlocation)
fk:dnumber is dnumber in Department
Project(pnumber, pname, plocation, dnum)
fk:dnum is dnumber in Department
Dependent(essn, dependent_name, sex, bdate, relationship)
fk: essn is ssn in Employee
Works_on(essn,pno,hours)
fk: essn is ssn in Employee; pno is pnumber in Project
我想檢索僅使用下列關係代數操作{財務部門的位置列表σ,π,∪,ρ, - ,× }。
到目前爲止,我有: πdlocation(σ部門(DNAME =「研究」))
我真的卡住了,迷茫......我不知道,如果它能夠做到這一點,而不等同操作。