=centercr
@ []Query Q 4.4.1: Find who was a driver, and the associated times, for a longer period than Ed, from 1/1/1982 to 12/31/1984.
Answer: ``(Di, 1/1/1982 – 12/31/1984)''
Category: (Projected, Not Empty) /
(Duration, Element, Explicit) /
(< >, Constant)
=centercr
@ []Query Q 4.4.2: Find who had been making the same salary for the longest time in
on Ed's birtday, and the length of that time.
Answer: ``(Di, 8/1/1984 – 7/1/1985)''
Category: (Projected, Not Empty) /
(Duration, Element, User-defined time) /
(=, Constant)
=centercr
@ []Query Q 4.4.3: Find who was the oldest typist on 12/31/1985, and the time during which
they had they been a typist.
Answer: ``(Ed, 4/1/1982 – 12/31/1985)''
Category: (Complete, Not Empty) /
(Duration, Element, Explicit) /
(=, Constant), (=, Foreign)
=centercr
@ []Query Q 4.4.4: Find the names of employees in the toy department who had worked
less than Di in that department as of 1/1/1985, and the amount of the difference in time.
Answer: ``(Ed, 1 month less)''
Category: (Projected, Not Empty) /
(Duration, Element, Explicit) /
(=, Constant), (< >, Single)
=centercr
@ []Query Q 4.4.5: Find the working employees who worked the least during 1987, and the times during which they worked (as based on the Employee relation).
Answer: ``(Ed, 1/1/1987 – 1/31/1987 U 4/1/1987 – 12/31/1987)''
Category: (Projected, Not Empty) / (Duration, Element, Explicit) / (Nothing)
=centercr
@ []Query Q 4.4.6: Who had at least two years of seniority in some department and
what were the periods of such seniority?
Answer: ``(Di, 01/01/82–01/01/90)''
Category: (Projected, Element, Derived) / (Duration, Element, Explicit) /