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author | Julian T <julian@jtle.dk> | 2021-09-30 11:51:29 +0200 |
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committer | Julian T <julian@jtle.dk> | 2021-09-30 11:51:29 +0200 |
commit | 4c9e4b9a65dc507fae927158ddc236f5e0632c01 (patch) | |
tree | fa7984742157ce1d7d134cf10b78ec88f0a1e759 | |
parent | 107f770ef91d94f1c4bd3a138d227c07d0908b95 (diff) |
Add assignments for dist
-rw-r--r-- | sem7/db/lec4.org | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/sem7/db/lec4.org b/sem7/db/lec4.org new file mode 100644 index 0000000..d39e4d4 --- /dev/null +++ b/sem7/db/lec4.org @@ -0,0 +1,62 @@ +* Opgave 1 + + Dette er opgave 2.1 fra bogen, på side 86. + +** Del opgave A + + #+BEGIN_QUOTE + Perform a horizontal fragmentation of relation EMP with respect /{ p1, p2 }/. + #+END_QUOTE + Her er /p1/ og /p2/ forklaret i opgaven. + + | ENO | ENAME | TITLE | + |-----+----------+-------------| + | E1 | J. Doe | Elect. Eng. | + | E3 | A. Lee | Mech. Eng. | + | E6 | L. Chu | Elect. Eng. | + | E7 | R. Davis | Mech. Eng. | + |-----+----------+-------------| + | E2 | M.Smith | Syst. Anal. | + | E5 | B. Casey | Syst. Anal. | + | E8 | J. Jones | Syst. Anal. | + + Desuden, wow hvor er tabel toolet her godt. + +** Del opgave B + + #+BEGIN_QUOTE + Explain why the resulting fragmentation /(EMP1, EMP2)/ does not fullfill the correctness of fragmentation. + #+END_QUOTE + + Well i guess thats because p1 and p2 did not include "Programmer", + so now if you join the partitions you wont get the full thing. + +** Del opgave C + + #+begin_quote + Modify the predicates p1 and p2 so that they partition EMP obeying the correctless rules of fragmentation. + To do this, modify the predicates, compose all minterm predicates and deduce the corresponding implications, + and then perform a horizontal fragmentation of EMP based on these minterm predicates. + Finally, show that the result has completeness, reconstruction, and disjointness properties + #+end_quote + + Okay so the predicates become: + + \begin{align*} +p_1 &= \mathtt{TITLE} \leq "Programmer" \\ +p_2 &= \mathtt{TITLE} > "Programmer" + \end{align*} + + | ENO | ENAME | TITLE | + |-----+-----------+-------------| + | E1 | J. Doe | Elect. Eng. | + | E3 | A. Lee | Mech. Eng. | + | E6 | L. Chu | Elect. Eng. | + | E7 | R. Davis | Mech. Eng. | + | E4 | J. Miller | Programmer | + |-----+-----------+-------------| + | E2 | M.Smith | Syst. Anal. | + | E5 | B. Casey | Syst. Anal. | + | E8 | J. Jones | Syst. Anal. | + + Nu kan vi se at completeness er opfyldt, og at ved at join de to partition får den originale tabel. |