Câu hỏi về Ngôn ngữ đại số quan hệ

Please choose the corresponding word/phrase to complete the statement: From the relational algebra operations, a query can be represented by

• A relational algebra expression

• A relational tree

• A relational expression and a relational operation tree

• A relational expression or a relational tree

Please choose the corresponding word/phrase to complete the statement: The operand in relational algebra operations is...

• Mathematical expressions

• Relations or relational algebra expressions

• Ensuring data consistency

• Ensuring data storage

What is the process of optimizing data query questions?

• The result of operations is uniquely represented by a relation

• It is necessary to transform reasonable questions

• Transforming questions so that time cost and memory usage are minimized

• Reducing the execution time cost of operations to the least

Which of the following statements is most accurate when talking about the UNION operation?

• The attributes of the union relation are the union of the attributes of the source relations

• The tuples of the union relation are the union of the tuples of the source relations

• The union of 2 compatible relations is a compatible relation with the source relations.

• The union of 2 relations is a relation.

Which of the following statements is most accurate?

• The difference of relations R and S, denoted as R - S, results in a relation containing all tuples in S but not in R

• The difference of relations R and S, denoted as R - S, results in a relation containing all tuples in S and in R

• The difference of relations R and S, denoted as R - S, results in an expression containing all tuples in S but not in R

• The difference of relations R and S, denoted as R - S, results in a relation containing all tuples in R but not in S

Which of the following statements is most accurate?

• The difference of relations R and S, denoted as S - R, results in a relation containing all tuples in S but not in R

• The difference of relations R and S, denoted as R - S, results in a relation containing all tuples in S and in R

• The difference of relations R and S, denoted as R - S, results in an expression

Given the database schema consisting of the relations: GIAOVIEN (MAGV, HOTEN, GIOITINH, NAMSINH, QUEQUAN); DETAI (MADT, TENDT, KINHPHI); THUCHIEN_DT (MAGV, MADT, NAMHOC, XEPLOAI). Use relational algebra to display information about the projects with a budget greater than 5000000. (Choose the most accurate and optimal answer)

• π TenDT (σ Kinhphi>5000000 (DETAI))

• σ Kinhphi>'5000000' (π TenDT (DETAI))

• σ Kinhphi>5000000 (π TenDT (DETAI))

• π TenDT (σ Kinhphi>'5000000' (DETAI))

Given the database schema consisting of the relations: GIAOVIEN (MAGV, HOTEN, GIOITINH, NAMSINH, QUEQUAN); DETAI (MADT, TENDT, KINHPHI); THUCHIEN_DT (MAGV, MADT, NAMHOC, XEPLOAI). Use relational algebra to display information about the names of the projects conducted in the academic year 2019-2020. (Choose the most accurate and optimal answer)

• π TenDT (DETAI DETAI.MADT=THUCHIEN_DT.MADT (σ Namhoc= '2019-2020' THUCHIEN_DT))

• π TenDT (σ Namhoc= '2019-2020' (DETAI DETAI.MADT=THUCHIEN_DT.MADT THUCHIEN_DT))

• σ Namhoc= '2019-2020' (π TenDT (DETAI DETAI.MADT=THUCHIEN_DT.MADT THUCHIEN_DT))

• π TenDT (DETAI DETAI.MADT=THUCHIEN_DT.MADT (σ Nam= '2019-2020' THUCHIEN_DT))

Given the database schema consisting of 3 relations: SINHVIEN (MASV, HOTEN, NAMSINH, QUEQUAN); PHONG (MAPHONG, TENPHONG, TANG); THUEPHONG (MASV, MAPHONG, NGAYTHUE, GIATHUE). Use relational algebra to find MAPHONG and the number of students who have rented. (Choose the most accurate and optimal answer)

• Maphong, Tenphong ℑ COUNT(MaSV) (π MAPHONG, TENPH, MASV (PHONG X THUEPHONG))

• Maphong ℑ COUNT(MaSV) (π MAPHONG, TENPHONG, MASV (PHONG X THUEPHONG))

• Maphong, Tenphong ℑ COUNT(MaSV) (PHONG PHONG.MAPHONG=THUEPHONG.MAPHONG THUEPHONG)

• Maphong ℑ COUNT(MaSV) (π MAPHONG, MASV (PHONG PHONG.MAPHONG=THUEPHONG.MAPHONG THUEPHONG))

Given the database schema consisting of 3 relations: SINHVIEN (MASV, HOTEN, NAMSINH, QUEQUAN); PHONG (MAPHONG, TENPHONG, TANG); THUEPHONG (MASV, MAPHONG, NGAYTHUE, GIATHUE).