Recent questions tagged relational-algebra

Consider the relation $\mathrm{Sailors}(\mathrm{sid},\mathrm{sname},\mathrm{rating},\mathrm{age})$ and the following TRC expression: $$\{S\mid \neg(S\in \mathrm{Sailors})...

Consider $\mathrm{Flights}(\mathrm{num},\mathrm{src},\mathrm{dst})$, where each tuple represents a directed flight from $\mathrm{src}$ to $\mathrm{dst}$.Let $\mathrm{F}_1...

Consider $\mathrm{Employee}(\mathrm{eid},\mathrm{name},\mathrm{salary})$, $\mathrm{Project}(\mathrm{pid},\mathrm{title},\mathrm{budget})$, and $\mathrm{WorksOn}(\mathrm{e...

Consider $\mathrm{Locations}(\mathrm{locationid},\mathrm{name},\mathrm{state},\mathrm{altitude})$$\mathrm{TreeCoverage}(\mathrm{locationid},\mathrm{treetype},\mathrm{year...

Consider $\mathrm{X}(\mathrm{A},\mathrm{B})$ and $\mathrm{Y}(\mathrm{B},\mathrm{C})$.Which expression is equivalent to $\sigma_{\mathrm{A}<15\land\mathrm{C}\geq10}(\mathr...

Consider two relations $\mathrm{r}$ and $\mathrm{s}$ with schemas $\mathrm{R(A,B,C)}$ and $\mathrm{S(A,B,D)}$, respectively.The query is $\pi_{\mathrm{A}}(\sigma_{\mathrm...

Consider $\mathrm{A}(\mathrm{c1},\mathrm{c2},\mathrm{c3})$ and $\mathrm{B}(\mathrm{c1},\mathrm{c2},\mathrm{c3})$, where $\mathrm{c1}$ is the primary key of each relation....

Let $\mathrm{R}(\mathrm{A},\mathrm{B})$ and $\mathrm{S}(\mathrm{A},\mathrm{B})$ be relations under set semantics.Which expression is not always equivalent to the others?$...

Consider :$$\begin{aligned}\begin{gathered}\mathrm{Customer} \\[-2pt]\begin{array}{|c|c|}\hline\mathrm{cid} & \mathrm{name} \\\hline1 & \mathrm{Joe} \\2 & \mathrm{Betty} ...

Consider $\mathrm{Homes}(\mathrm{home\_id},\mathrm{city},\ldots)$ and $\mathrm{Transactions}(\mathrm{home\_id},\mathrm{sale\_price},\ldots)$.We want every home in Berkele...

Consider $ \mathrm{MEMBER}(\mathrm{personName}, \mathrm{groupName}) $ and $ \mathrm{PICTURE}(\mathrm{groupName}, \mathrm{picture}) $.Every person belongs to at least one ...

Consider$\mathrm{Player}(\mathrm{playerID}, \mathrm{name}, \mathrm{position}, \mathrm{height}, \mathrm{weight}, \mathrm{team})$$\mathrm{Game}(\mathrm{gameID}, \mathrm{hom...

Consider$\mathrm{Student}(\mathrm{sid}, \mathrm{sname}, \mathrm{major})$$\mathrm{EnrolledIn}(\mathrm{sid}, \mathrm{cid}, \mathrm{grade})$$\mathrm{Course}(\mathrm{cid}, \m...

Let $\mathrm{R}(\mathrm{X},\mathrm{Y})$ and $\mathrm{S}(\mathrm{Y})$.Which expression is equivalent to $\mathrm{R} \div \mathrm{S}$ without using the division operator?$\...

Consider$\mathrm{Suppliers}(\mathrm{SID}, \mathrm{sname}, \mathrm{address})$$\mathrm{Parts}(\mathrm{PID}, \mathrm{pname}, \mathrm{color})$$\mathrm{Catalog}(\mathrm{SID}, ...

Consider$\mathrm{Student}(\mathrm{snum},\mathrm{sname},\mathrm{major},\mathrm{level},\mathrm{age})$$\mathrm{Class}(\mathrm{name},\mathrm{meets\_at},\mathrm{room},\mathrm{...

Assume the expressions below are schema-valid and relations use set semantics.Which of the following are always true?$(\mathrm{R}\bowtie\mathrm{S})\bowtie\mathrm{T}=(\mat...

Consider the relations:$\mathrm{Authors(au\_id,au\_lname,au\_fname,phone,address,city,state,zip)}$$\mathrm{TitleAuthors(au\_id,title\_id,au\_ord,royaltyshare)}$$\mathrm{T...

Consider the relations:$\mathrm{Locations(locationid,name,state,altitude)}$ and $\mathrm{FallColors(week,year,locationid,color,peakpercent)}$.We want locations in New Y...

Consider the relations:$\mathrm{Posts(pid,folder,summary)}$ and $\mathrm{Postings(post,position,user,ptext)}$.Let $\mathrm{R_1}$ and $\mathrm{R_2}$ be two renamed copies ...

Consider the relation:$\mathrm{Marks(studentID,~courseID,~courseType,~score)}$Let, $\mathrm{M_1=\rho_{M_1}(Marks)}$ and $\mathrm{M_2=\rho_{M_2}(Marks)}$.Which expression ...

Consider the relations:$\mathrm{Users(username, name, email, password, address)}$and$\mathrm{FriendsWith(username, username2, sincewhen)}$.A friendship tuple indicates th...

Consider the relations:$\mathrm{STUDENT(name,regno,gpa,level,dept)}$$\mathrm{COURSE(cno,cname,dept)}$$\mathrm{TAKE(regno,cno)}$Using only the basic relational algebra ope...

Consider $R(a,b)$ and $S(c,d)$.Which relational algebra expression is equivalent to:SELECT a, d FROM R, S WHERE R.a 10 AND R.b = S.c;Use only the basic operators.$\pi_{a...

Let $R$ and $S$ be union-compatible relations.Which expression computes $R\cap S$ using only union and set difference?$(R\cup S)-((R-S)\cup(S-R))$ $(R\cup S)-(R-S)$ $(R-S...

Consider $\text{parts(pno, pname, price)}$.Which relational algebra expression returns exactly the names of all parts whose price is greater than $\$200$?$\pi_{\text{pnam...

Which of the following statements are correct?The HAVING CLAUSE is an optional clause which tells Oracle to group rows based on distinct values that exist for specified c...

Consider the given relations $X, Y$ and $Z$. The relation $X$ has three columns $P, Q$ and $R$. The relation $Y$ has three columns $P, Q$ and $S$. The relation $Z$ has tw...