Relational Algebra Exercise

Given database schemas:

Product$($maker$,$ model, type$)$

PC$($model$,$ speed, ram, hd$,$ price$)$ Laptop$($model$,$ speed, ram, hd$,$ screen, price$)$ Printer$($model$,$ color, type, price$)$

Questions:

a$)$ What PC models have a speed of at least $3\mathrm{.}00?$

R$1=$select $($speed $>=3\mathrm{.}0)($PC$)$ R$2=$ project $($model$)($R$1)$

b$)$ Which manufacturers make laptops with a hard disk of at least $100$GB$?$ R$1=$ select $($hd $=>100)($laptop$)$

R$2=$natural$\_$join $($Product$,$ R$1)$ R$3=$ project $($make$)($R$2)$

c$)$ Find the model and price of all products $($of any type$)$ made by manufacturer B$.$ R$1=$ Project $($model$)($select $($maker $=\text{'}$B$\text{'})($Product$))$

R$2=$ Project $($model$,$ price$)($PC$)$

R$3=$Project $($model$,$ price$)($laptop$)$ R$4=$ Project $($model$,$ price$)($printer$)$ R$5=$ R$2$ U R$3$ U R$4$

R$6=$ natural $\_$join $($R$1,$ R$5))$

Exercise a

R$1$:$=0$speed $>=30\mathrm{.}0($PC$)$

R$2$:$=$ model $($R$1)$

Exercise b

R$1$:$=$ Ond $>=10($Laptop$)$ R$2$:$=$ Product DA $($R$1)$

R$3=$: Mmaker $($R$2)$

Exercise c

R$1$:$=0$maker$=$B $($Product DA PC$)$

R$2=$: $0$ maker$=($Product $4$ R$3$ :$=0$maker$=($Product $*$

R$4$:$=$ model, price $($R$1)$

R$5$:$=$ model, price $($R$2)$

R$6$: $=$ model, price $($R$3)$ R$7$:$=$ R$4$ UR$5$ U R$6$

Laptop$)$ Printer$)$

Exercise d

R$1$:$=$ Ocolr $=$true AND ytpe $=$laser $($Printer$)$

R$2$:$=$ model $($R$1)$

Exercise e

R$1$:$=$ Otype$=$laptop $($Product$)$

R$2$:$=0$type$=$Pc$($Product$)$ R$3=$: TmakerR$1)$

R$4$:$=$ maker $($R$2)$ R$5$:$=$ R$3-$ R$4$

Exercise f

R$1$:$=$ Ppc$1($PC$)$

R$3$:$=$ R$1$ DX $($PC$.$hd $=$PC$.$hd AND PC$1$m$.$ odel $><$ PC$2.$model$)$ R$2$ R$4$ :$=$ n d $($R$3)$

Exercise g

R$1$:$=$ Ppc$($PC$)$

R$2$:$=$ Ppc$2($PC$)$

R$3$:$=$ R$1/$X $($P$1$speed $=$PC$2$ sped AND PC$1.$ amr $=$PC$2$ra$.$m ANDPC$1.$ model