UV Distributed Information Management
Summer semester 2022
Questionnaire Assignment 1
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The purpose of this questionnaire is to deepen the student's understanding of
assignment 1 and the topics covered in the lecture. The main focus will be the
*correctness* and the *quality* of an answer, not its length. For some
questions, we will provide rough hints to give you a head start.

You are free to answer the questions directly in this textfile or use another
editor/word processor. The following file formats will be accepted for the
submission: .txt, .pdf, .odt, .doc, .docx. Please note that other file formats
will result in 0 points (for this questionnaire). The preferred file formats are
.txt and .pdf (most word processors support an export as PDF file). In any case,
please make sure that the questions/answers are named/numbered properly!

This questionnaire will be discussed during the after-assignment meeting. Before
the meeting starts, the group will be informed about the preliminary points by
the instructor (either at the beginning of the meeting or via Blackboard). The
final points will be set after the meeting. This questionnaire contributes a
maximum of 8 points to the overall points of assignment 1.

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Question F1:
Change query Q2 such that it only reports movies named 'The Avengers' that
started after 1990 (startYear). Please formulate the SQL query in the answer.
For query Q2, we refer to the assignment description. 

Answers A1:
<Your answer can go here>

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Question F2:
In the lecture, we discussed consistency constraints. Name and describe at least
one consistency constraint of table 'names'. Is this a constraint on a column or
on the entire table?

Hints:
You can either look at the 'CREATE TABLE' statement in the file create_db.sql or
you can use the command '\d names;' to get some information about the table
(including the consistency constraints).

Answers A2:
<Your answer can go here>

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Question F3:
In the lecture, we discussed three levels of abstraction (bottom up): (a) the
physical level, (b) the logical level, and (c) the view level. Name the level we
operate on for this assignment. Please also justify your choice.

Answers A3:
<Your answer can go here>

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Question F4:
Consider the query plan of query Q4. Try to understand and describe what
information is provided by the query plan. Most importantly, what is the link
between the query and the query plan. Is the query plan declarative or
procedural?

Hints:
Your answer should be on an intuitive level, there is no need to understand all
the details (i.e., numbers) that are shown in the query plan. To understand the
terminology, we recommend to read the PostgreSQL documentation of the 'EXPLAIN'
statement (in particular, the first 3 explanations in the Basics section):
https://www.postgresql.org/docs/current/using-explain.html.
'Seq Scan' refers to a so-called sequential scan, that is, the database system
will simply read all the data of the respective table (from start to end).

Answers A4:
<Your answer can go here>