set-difference

Consider the following three relations in a relational database. Employee ( $$\underline {eld} $$ , Name), Brand ( $$\underline {bld} $$ , bName), Own ( $$\underline {eld} $$ , $$\...

Consider a complete binary tree with 7 nodes. Let A denote the set of first 3 elements obtained by performing Breadth-First Search (BFS) starting from the root. Let B denote the se...

Suppose that L 1 is a regular and L 2 is a context-free language, Which one of the following languages is NOT necessarily context-free?

Suppose $$𝑈$$ is the power set of the set $$S = \left\{ {1,2,3,4,5,6,} \right\}$$. For any $$T \in U,$$ let $$\left| T \right|$$ denote the number of elements in $$𝑇$$ and $$T'$$...

Consider the relational schema given below, where eId of the relation dependent is a foreign key referring to empId of the relation employee . Assume that every employee has at lea...

Suppose R 1 ( A, B) and R 2 ( C, D) are two relation schemas. Let r 1 and r 2 be the corresponding relation instances. B is a foreign key that refers to C in R 2 . If data in r 1 a...

Let $${L_1}$$ recursive language. Let $${L_2}$$ and $${L_3}$$ be languages that are recursively enumerable but not recursive. Which of the following statement is not necessarily tr...

Information about a collection of students is given by the relation studInfo(studId, name, sex) . The relation enroll(studId, courseId) gives which student has enrolled for (or tak...

Let E, F and G be finite sets. Let $$X = \,\left( {E\, \cap \,F\,} \right)\, - \,\left( {F\, \cap \,G\,} \right)$$ and $$Y = \,\left( {E\, - \left( {E\, \cap \,G} \right)} \right)\...

Let $$A$$, $$B$$ and $$C$$ be non-empty sets and let $$X = (A - B) - C$$ and $$Y = (A - C) - (B - C)$$ Which one of the following is TRUE?

Let R 1 ( A, B, C) and R 2 ( D, E) be two relation schema, where the primary keys are shown underlined, and let C be a foreign key in R 1 referring to R 2 . Suppose there is no vio...

Give a relational algebra expression using only the minimum number of operators from $$\left( { \cup ,\, - } \right)$$ which is equivalent to $$R \cap S$$.