Book )) SQL : SELECT Isbn,Bname FROM Publisher NATURAL JOIN Editor NATURAL JOIN Book WHERE Pname =‘ XNJDP ’ AND Ename =‘ MTQ ’②关系代数表达式: π Isbn,Bname (σ Agender =男( Publisher Author Book CB )∩σ Pname = XNJDP ( Publisher Author Book CB ) ∩σ Pdate >= 2008-01-01 ( Publisher Author Book CB )∩σ Pdate <= 2008-12-31 ( Publisher Author Book CB )) SQL : SELECT Isbn,Bname FROM Publisher NATURAL JOIN Author NATURAL JOIN Book NATURAL JOIN CB WHERE Agender =‘男’ AND Pname =‘ XNJDP ’ AND Pdate >= ‘ 2008-01-01 ’ AND Pdate <= ‘ 2008-12-31 ’③关系代数表达式: π Isbn,Bname (σ Egender =女( Publisher Editor Book )∩σ Bprice >= 20( Publisher Editor Book )∩σ Bprice <= 40( Publisher Editor Book )) SQL : SELECT Isbn,Bname FROM Publisher NATURAL JOIN Editor NATURAL JOIN Book WHERE Egender =‘女’ AND Bprice >= 20 AND Bprice <= 40
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