3. Consider the following tables for undergraduate and graduate students. Using

Question

3. Consider the following tables for undergraduate and graduate students. Using relational algebra, what will be result of the following: (tables show in picture uploaded) a) The number of rows resulting from UGrad - Grad b) The number of columns resulting from UGrad x Grad c) The number of rows resulting from p_sName, GPA (UGrad) d) The number of rows resulting from UGrad È Grad e) The number of rows resulting from UGrad Ç Grad f) The number of columns resulting from p_GPA (UGrad) g) The number of rows resulting from UGrad Grad h) The number of columns resulting from UGrad Ç Grad i) The number of rows resulting from p_GPA (UGrad) j) The number of rows resulting from UGrad x Grad UGrad table SID sName login GPA 101 John jsmith 3.9 102 Mary Mary33 3.65 103 Paul ppp 3.5.5 104 James J132 3.5:5 Grad table SID sName login GPA 106 Ralph star 3.12 102 Mary Mary33 3.65 103 Paul lpaul 3.02 104 Nancy nan 3.10

Explanation / Answer

(a) number of rows in UGrad - Grad = 3          

which is row with id 101, 103, 104. Since, row with id 102 is common in both. so it is eliminated.

(b) number of columns in UGrad x Grad = columns(UGrad)+columns(Grad) = 4 + 4 =8

(c) number of rows in p_sName,GPA(UGrad) = 4

since, projection operator doesn't affect number of rows.

(d) number of rows in UGrad È Grad = 1 (where È represents natural join.)

because, there is only one row such that UGrad.sID = Grad.sID ^ UGrad.sName = Grad.sName^ UGrad.login = Grad.login ^ UGrad.GPA = Grad.GPA

(e) number of rows in UGrad Ç Grad = 1 where Ç represents intersection operator.

because there is only one row common in UGrad and Grad

(f) number of columns in p_GPA(UGrad) = 1

(g) Operator missing in between UGrad and Grad.

or, if u want to ask number of rows in UGrad or in Grad, then it is 4.

(h) number of columns in UGrad Ç Grad = 4

(i) number of rows in p_GPA (UGrad) = 3

which is ( 3.9, 3.65, 3.55 )

(j) number of rows in UGrad x Grad = nrows(UGrad)*nrows(Grad) = 4 * 4 =16

where x represents cross product.

Related Questions

Navigate

• Browse (All)
• Browse 3
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.