09 Relational Calculus
Tuple Relational Calculus (TRC)¶
Display loans over $1200
\[ \{ t | t \in \text{loan} \land t[\text{amount}] > 1200 \} \]
Display loan number for every loan > $1200
\[ \begin{aligned} \{ t | \exists s \in \text{loan} ( \\ && t[\text{loanNumber}] &= s[\text{loanNumber}] \\ && \land s[\text{amount}] &> 1200 \\ ) \} \end{aligned} \]
Names of customers having loan at Perry branch ”
\[ \begin{aligned} \{ & t | \textcolor{purple}{ \underbrace{ \exists b \in \text{borrower} \land \exists l \in \text{loan} }_\text{from}} ( \\ & \textcolor{hotpink}{ \underbrace{t.cn = b.cn}_\text{select}} , \\ & \textcolor{orange}{\underbrace{l.bn = \text{“Perry"} \land l.ln = b.ln}_\text{where} \\ } &) \} \end{aligned} \]
Domain Relational Calculus (DRC)¶
Display loans over $1200
\[ \{ \textcolor{purple}{\underbrace{<l, b, a>}_\text{select}} | \textcolor{hotpink}{\underbrace{<l, b, a> \in \text{loan}}_\text{from}} \land \textcolor{orange}{\underbrace{a > 1200}_\text{where}} \} \]
Display names of customers having loan > $1200
\[ \{ <n> | \exists l, b, a something \} \]