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34 lines
1.1 KiB
TeX
34 lines
1.1 KiB
TeX
\documentclass[12pt]{article}
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\title{EDABA Homework 2}
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\author{Krzysztof Rudnicki, 307585}
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\begin{document}
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\maketitle
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\section{Task 1}
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Find names of Students attending \underline{at least 3 lectures}
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\[ LS1 := LS(L\# \rightarrow L1\#) \]
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\[ LS2 := LS(L\# \rightarrow L2\#) \]
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\[ R1 := LS \bowtie LS1 \]
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\[ R2 := \sigma_{L\# \neq L1\#} (R1) \]
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\[ R3 := R2 \bowtie LS2 \]
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\[ RF := \sigma_{L\# \neq L2\# \: AND \: L1\# \neq L2\#} (R1) \]
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\[ S1 = \pi_{S\#}(RF) \]
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\[ RES = \pi_{SName} (S1 \bowtie ST) \]
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\section{Task 2}
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Find names of Students attending \underline{at least 2 lectures having ECTS > 5}
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\[ LS51 := LS \bowtie \pi_{L\#}(\sigma_{ECTS>5}(L)) \]
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\[ LS52 := LS51(L\# \rightarrow L52\#) \]
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\[ R1 := LS51 \bowtie LS52 \]
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\[ R2 := \sigma_{L\# \neq LS52\#} (R1) \]
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\[ R3 := \pi_{S\#}(R2) \]
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\[ Res := \pi_{SName,S\#}(ST \bowtie R3) \]
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\section{Task 3}
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\underline{Find the oldest students}
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\[ R1 := \pi_{S\#, Age}(ST) \]
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\[ R2 := \pi_{S\#, Age}(ST) \]
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\[ R3 := R1xR2(AGE \rightarrow AGE2) \]
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\[ R4 := \sigma_{R1.age < R2.age2} (R3) \]
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\[ R5 := \pi_{S\#}(ST) - \pi_{S1}(R3) \]
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\end{document} |