c/1/D1

SELECT TenCT, MAX(Luong)
FROM(SELECT CungTP.*, LamViec.Luong, CongTy.MaCT, CongTy.TenCT
    FROM (SELECT DISTINCT NV.MaNV, NV.TenNV
        FROM NhanVien NV, NhanVien QL, QuanLy
        WHERE NV.MaNV=QuanLy.MaNV
            AND QL.MaNV=QuanLy.MaQL
            AND NV.ThanhPho=QL.ThanhPho
            AND NV.Pho=QL.Pho) CungTP, LamViec, CongTy
    WHERE  CungTP.MaNV = LamViec.MaNV
        AND LamViec.MaCongTy=CongTy.MaCT) NV_LV_CT
GROUP BY TenCT,MaCT