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Material for Database Class.
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Almost done with the homeworks! f82824a2ca9769a0ecf8fc75d6bf1cae1ef3c7a4 aubert@math.cnrs.fr 2018-05-20 05:23:43
Travail sur intégration des exos dans les notes. c5a6676f85953c7bec9bb2de99bed3552ecf52af aubert@math.cnrs.fr 2018-05-20 05:04:30
Les exercises compilent :-) d4230fce5210d1d8905a42d11634e49e82217541 aubert@math.cnrs.fr 2018-05-19 19:09:56
Progrès sur exercises. 40dd86cdc624209a2282d4437921f46325c2cfa1 aubert@math.cnrs.fr 2018-05-19 18:34:07
Working on exercises. 42549c8d28249f1ecf85dd21f6d004ae63c533ad aubert@math.cnrs.fr 2018-05-19 05:43:04
Working on incorporating the exercises. f32148faeb8b11425fe9a57770db9bc85ae02c34 aubert@math.cnrs.fr 2018-05-19 04:51:37
working on sum for exo. 5fb55d2c31b06161ade3a7cae707485d8c02447a aubert@math.cnrs.fr 2018-05-18 21:12:56
Adding various small notes. 5eac6e0b19441fca9a3f70f239d5cbbc4d769976 aubert@math.cnrs.fr 2018-05-17 20:37:14
First pass over! ea1e4f6ddabd91287d10384dc8f28565a762526b aubert@math.cnrs.fr 2018-05-17 19:26:28
Working on notes on normal forms. 58bfcedc6bd6336592a5f93a43ffc0aaf64fa8f6 aubert@math.cnrs.fr 2018-05-16 16:40:12
Initial commit, draft of lecture notes. 200d2739bca881d60c7c9381b16f5a4d6384ff29 aubert@math.cnrs.fr 2018-05-16 15:35:36
Commit f82824a2ca9769a0ecf8fc75d6bf1cae1ef3c7a4 - Almost done with the homeworks!
Author: aubert@math.cnrs.fr
Author date (UTC): 2018-05-20 05:23
Committer name: aubert@math.cnrs.fr
Committer date (UTC): 2018-05-20 05:23
Parent(s): c5a6676f85953c7bec9bb2de99bed3552ecf52af
Signer:
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Signing status: N
Tree: 4d661388b61c29b9cfbd6bec3f6198406afdc5e2
File Lines added Lines deleted
exercises/sum.md 0 487
notes/00_sum.md 466 11
File exercises/sum.md changed (mode: 100644) (index c6f2a50..c0cafe5)
... ... pandoc sum.md --pdf-engine=xelatex --toc --filter pandoc-numbering --top-level-d
45 45
46 46 --> -->
47 47
48
49
50 Problem +.#
51
52
53
54 %%% 06
55
56
57 Exercise +.#
58 ~ Consider the relation \(R(A, B, C, D, E)\) and the functional dependencies \( \{A, B\} \to C, B \to D, C \to E\).
59 Answer the following:
60
61 1. \(A\) by itself is not a primary key, but what is the only key that contains \(A\)?
62 2. List the non-prime attributes.
63 3. This relation is not in 2NF: what transformation can you operate to obtain a 2NF?
64 4. One of the relation you obtained at the previous step is likely not to be in 3NF.
65 Can you normalize it?
66 If yes, how?
67
68 Solution +.#
69
70 \(\{A, B\}\),
71
72 \(C, D, E\),
73
74 \(R_1(A, B, C, E)\) and \(R_2(B, D)\)
75
76 \(R_1(A, B, C)\), \(R_2(C, E)\) and \(R_3(B, D)\)
77
78
79
80 Exercise +.#
81 ~ What are the two different categories of U.M.L. diagram?
82
83
84 Solution +.#
85 ~ Behaviour and structure
86
87
88 Exercise +.#
89 ~ Can a \texttt{C++} developer working on Linux and a \texttt{Java} developer working on MacOS use the same class diagram as a basis to write their programs?
90 Justify your answer.
91
92
93 Solution +.#
94 ~ Yes, U.M.L. diagram is language-independent and platform-independent.
95
96
97 Exercise +.#
98 ~ What kind of diagram should we use if we want to \(…\)
99
100 1. describe the functional behavior of the system as seen by the user?
101 2. capture the flow of messages in a software?
102 3. represent the workflow of actions of an user?
103
104 Solution +.#
105 ~ 1. Use-case
106 2. Sequence diagram
107 3. Activity diagram
108
109 Exercise +.#
110 ~ Name two reasons why one would want to use a U.M.L. class diagram over an E.-R. diagram to represent a conceptual schema.
111
112
113 Solution +.#
114 ~ To use direction for association, to have a common language with someone less knowledgeable of other diagrammatic notations.
115 For the concept of integration.
116
117
118 Exercise +.#
119 ~ Consider the following diagram:
120
121 \begin{tikzpicture}[scale = 0.8]
122 \begin{class}[text width=7cm]{Flight}{0,0}
123 \attribute{flightNumber : Integer}
124 \attribute{departureTime : Date}
125 \attribute{flightDuration : Minutes}
126 \attribute{departingAirport : String}
127 \attribute{arrivingAirport : String}
128 \operation{delayFlight(numberOfMinutes : Minutes)}
129 \operation{getArrivalTime( ) : Date}
130 \end{class}
131 \begin{class}{Plane}{11, -0.8}
132 \attribute{airPlaneType : String}
133 \attribute{maximumSpeed : MPH}
134 \attribute{maximumDistance : Miles}
135 \attribute{tailID : String}
136 \end{class}
137 \association{Plane}{}{0..1}{Flight}{0..*}{}
138 \end{tikzpicture}
139
140 Give the number of attributes for both classes, and suggest two operations for the class that doesn't have any.
141 Discuss the multiplicities: why did the designer picked those values?
142
143
144 Solution +.#
145 ~ \(5\) and \(4\).
146
147 getLastFlightNumber() : Integer
148
149 stMaximumSpeed(MPH) : void
150
151 A flight could be assigned to no plane, and a plane could not be assigned to a flight.
152
153 A plane can be assigned to multiple (or no) flights, but a flight must have at most one plane (and could have none).
154
155
156 Exercise +.#
157 ~ Briefly explain the difference between an aggregation and a composition association.
158
159
160 Solution +.#
161 ~ Aggregation: associated class can have an existence of its own.
162
163 Composition association: class doesn't exist without the association.
164
165
166 Exercise +.#
167 ~ How is generalization (or inheritance) represented in a U.M.L. class diagram?
168 Why is such a concept useful?
169
170
171 Solution +.#
172 ~ \tikz{\draw[>=open triangle 60,->] (0,0) to (1,0);}
173 Because it avoids redundancy.
174
175
176 Exercise +.#
177 ~ Convert the following E.R. diagram into a U.M.L. class diagram:
178
179 \begin{tikzpicture}[node distance=8em]
180 \node[entity] (person) {PILOT};
181 \node[attribute] (pid) [left of=person] {\key{ID}} edge (person);
182 \node[attribute] (name) [above left of=person] {Name} edge (person);
183 \node[attribute] (phone) [above of=person] {Experience} edge (person);
184
185 \node[relationship] (drives) [below of=person] {ASSIGNED\_TO} edge node[right, pos=0.1] {$N$} (person);
186 \node[entity] (plane) [below of=drives] {PLANE} edge [total] node[right, pos=0.7] {$1$} (drives);
187 \node[attribute] (make) [left of=plane] {\key{TailID}} edge (plane);
188 \node[attribute] (maxS) [below left of =plane] {MaxSpeed} edge (plane);
189 \node[attribute] (airPlaneType) [below of = plane] {AirPlaneType} edge (plane);
190 \end{tikzpicture}
191
192 Problem +.#
193
194 \label{probMYSQLW}
195 Consider the following E.R. schema for the CAR\_INFO database:
196
197 \begin{tikzpicture}[node distance=8em]
198 \node[entity] (person) {PERSON};
199 \node[attribute] (pid) [left of=person] {\key{ID}} edge (person);
200 \node[attribute] (name) [above left of=person] {Name} edge (person);
201 \node[multi attribute] (phone) [above of=person] {Phone} edge (person);
202 \node[attribute] (address) [above right of=person] {Address} edge (person);
203 \node[attribute] (street) [above right of=address] {Street} edge (address);
204 \node[attribute] (city) [right of=address] {City} edge (address);
205 %\node[derived attribute] (age) [right of=person] {Age} edge (person);
206
207 \node[relationship] (drives) [below right of=person] {DRIVES} edge node[above, pos=0.1] {$1$} (person);
208 \node[entity] (car) [below left of=drives] {CAR} edge node[above, pos=0.7] {$1$} (drives);
209 \node[attribute] (make) [left of=car] {Make} edge (car);
210 \node[attribute] (year) [below left of =car] {Year} edge (car);
211 \node[attribute] (brand) [below of =car] {Brand} edge (car);
212
213 \node[relationship] (seats) [below left of=person] {SEATS\_IN} edge node[above, pos=0.1] {$N$} (person);
214 \draw (seats) edge node[above, pos=0.3] {$1$} (car);
215 \node[attribute] (position) [left of=seats] {Position} edge (seats);
216
217 \node[ident relationship] (insured) [right of=car] {INSURED} edge node[above, pos=0.3] {$1$} (car);
218 \node[weak entity] (insurance) [right = 1cm of insured] {CAR\_INSURANCE} edge[total] node[above, pos=0.7] {$N$} (insured);
219 \node[attribute] (amount) [above of =insurance] {Covered Amount} edge (insurance);
220 \node[attribute] (policy) [above right of =insurance] {Policy Number} edge (insurance);
221 \node[attribute] (company) [below right of =insurance] {Company Name} edge (insurance);
222 \end{tikzpicture}
223
224 Note that a car can have at most one driver, \(N\) passengers, \(N\) insurances, and that car insurances exist only if they are "tied up" to a car (i.e., they are weak entities, and their identifying relationship is called "Insured").
225
226 1. Find the key attribute for "Car", and the partial key for "Car Insurance". If you can't think of any, add a dummy attribute and make it be the key.
227 2. Convert that E.-R. diagram to a relational database schema.
228 3. Convert the E.-R. diagram to a U.M.L. class diagram. Comparing Figure 7.16 with Figure 7.2 from your textbook should guide you.
229
230 Solution +.#
231 ~ For "Car", we need to create an attribute, like "vin".
232 For "Car Insurance", "Policy Number" is perfect.
233
234 \colorlet{lightgray}{gray!20}
235
236 \begin{tikzpicture}[relation/.style={rectangle split, rectangle split parts=#1, rectangle split part align=base, draw, anchor=center, align=center, text height=3mm, text centered}]\hspace*{-0.3cm}
237
238 % RELATIONS
239
240 \node (phonetitle) {**PHONE**};
241
242 \node [relation=2, rectangle split horizontal, rectangle split part fill={lightgray!50}, anchor=north west, below=0.6cm of phonetitle.west, anchor=west] (phone)
243 {\underline{id}%
244 \nodepart{two} \underline{number}
245 };
246
247 \node [below=1.3cm of phone.west, anchor=west] (persontitle) {**PERSON**};
248
249 \node [relation=6, rectangle split horizontal, rectangle split part fill={lightgray!50}, below=0.6cm of persontitle.west, anchor=west] (person)
250 {\underline{id}%
251 \nodepart{two} Name
252 \nodepart{three} Street
253 \nodepart{four} City
254 \nodepart{five} Seat
255 \nodepart{six}{Position}
256 };
257
258 \node [below=1.1cm of person.west, anchor=west] (cartitle) {**CAR**};
259
260 \node [relation=5, rectangle split horizontal, rectangle split part fill={lightgray!50}, anchor=north west, below=0.6cm of cartitle.west, anchor=west] (car)
261 {\underline{Vin}%
262 \nodepart{two} Make
263 \nodepart{three} Year
264 \nodepart{four} Brand
265 \nodepart{five} Driver
266 };
267
268 \node [below=1.4cm of car.west, anchor=west] (carinsurancetitle) {**CAR INSURANCE**};
269
270 \node [relation=4, rectangle split horizontal, rectangle split part fill={lightgray!50}, anchor=north west, below=0.6cm of carinsurancetitle.west, anchor=west] (carinsurance)
271 {\underline{Policy Number}%
272 \nodepart{two} Covered Amount
273 \nodepart{three} Company Name
274 \nodepart{four} Insured Car
275 };
276
277 % FOREIGN KEYS
278
279 \draw[-latex] (phone.one south) -- ++(0,-0.2) --++(7,0) --++(0, -2) -| ($(person.one south) + (0.2,0)$);
280 %\draw[-latex] (person.five south) -- ++(0,-0.2) --++(3,0) --++(0, -2) -| ($(car.one south) + (-0.2,0)$);
281 \draw[-latex] (carinsurance.four south) -- ++(0,-0.2) --++(2,0) --++(0, 1.75) -| ($(car.one south) + (0.1,0)$);
282 \draw[-latex] (car.five south) -- ++(0,-0.2) --++(2,0) --++(0, 1.5) -| ($(person.one south) + (-0.1,0)$);
283 \end{tikzpicture}
284
285
286 \begin{tikzpicture}[scale = 0.8]
287 \node (person) at (0,0){\begin{tabular}{| r l |}
288 \hline
289 \multicolumn{2}{| c |}{**Person**}\\
290 \hline
291 id &: String\\
292 name &: String\\
293 address &: Street\\
294 & City\\
295 \hline
296 getAge()&: Int\\
297 \hline
298 \end{tabular}
299 };
300 \node (phone) at (8, 1){\begin{tabular}{| r l |}
301 \hline
302 \multicolumn{2}{| c |}{**Phone**}\\
303 \hline
304 number &: String\\
305 \hline
306 \end{tabular}
307 };
308 \draw[open diamond-] (person) -- node[above, pos=0.1]{\(0..\star\)} node[above, pos=0.9]{\(1..1\)} (phone);
309 \node (car) at (8, -3){\begin{tabular}{| r l |}
310 \hline
311 \multicolumn{2}{| c |}{**Car**}\\
312 \hline
313 vin &: String\\
314 make &: String\\
315 year &: Year\\
316 brand &: String\\
317 \hline
318 \end{tabular}
319 };
320 \draw[-] ($(person)+(2.5,-0.5)$) -- node[above, pos=0.1]{\(0..1\)} node[above, pos=0.5]{drives} node[above, pos=0.9]{\(0..1\)} (car);
321 %\draw[-] (person) -- node[below, pos=0.1]{\(0..1\)} node[below, pos=0.9]{\(0..4\)} ($(car)+(-2.5, 0.5)$);
322 \node (seat) at (3.5, -5){\begin{tabular}{| r l |}
323 \hline
324 \multicolumn{2}{| c |}{**Seats In**}\\
325 \hline
326 position &: String\\
327 \hline
328 \end{tabular}
329 };
330 \draw[dashed] (seat) -- (3.5, -1.6);
331
332 \node (insu) at (14.3, -2){\begin{tabular}{| r l |}
333 \hline
334 \multicolumn{2}{| c |}{**Car Insurance**}\\
335 \hline
336 policy number &: String\\
337 covered amount &: int\\
338 compagny name &: String\\
339 \hline
340 \end{tabular}
341 };
342
343 \draw[diamond -] (car) -- node[above, pos=0.1]{\(0..\star\)} node[above, pos=0.9]{\(1\)} (insu);
344 \end{tikzpicture}
345
346
347
348 Problem +.#
349
350 In this exercise, we will install and explore the basic functionalities of MySQL Workbench, which is a cross-platform, open-source, and free graphical interface for database design.
351
352 1. Install MySQL Workbench: use your package manager, or download the binaries from \url{https://dev.mysql.com/downloads/workbench/}.
353 2. Once installed, execute the software. Under the panel "MySQL Connections", you should see your local installation listed as "Local instance 3306". Click on the top-right corner of that box, and then on "Edit Connections". Alternatively, click on "Database", on "Manage Connections", and then on "Local instance 3306".
354 3. Check that all the parameters are correct. Normally, you only have to change the name of the user to "testuser", and leave the rest as it is. Click on "Test the connection", and enter your password (which should be "password") when prompted. If you receive a warning about "Incompatible/nonstandard server version or connection protocol detected", click on "Continue anyway".
355 4. Now, click on the box "Local instance 3306", and enter your password. A new tab appears, you can see the list of schemas in the bottom part of the left panel.
356 5. Click on "Database", and then on "Reverse Engineering" (or hit \texttt{ctrl} + \texttt{r}), click on "next", enter your password, and click on "next". You should see the list of the schemas stored in your database. Select one (any one, we are just exploring the functionalities at that point), click on "next", and then click on "execute", "next", and "close".
357 6. You're back on the previous view, but you should now see "E.E.R. diagram" on the top of the middle panel. Click on "E.E.R. diagram" twice, scroll down if needed, and you should see the E.E.R. diagram.
358 7. This diagram isn't exaclty an E.-R. diagram, and it's not a U.M.L. diagram either. Yet, you should still be able to understand parts of it, and should try to modify it. Make some relations mandatory, change their name, add an attribute, change the name of another, insert a couple of elements in an entity, add a row in a table, etc. Make sure you understand the meaning of the lines between the entities.
359 8. Once you're done, try to "Forward Engineer" by hitting "Ctrl" + "G". Click on "next" twice, enter your password, click on lick on "next" once more, and you should see the \texttt{SQL} code needed to produce the table you just designed using the graphical tool.
360
361
362 Problem +.#
363
364 \emph{This problem requires you to have successfully completed Problem~ \ref{probMYSQLW} and Problem~ \ref{probERtoREL}.}
365
366 Using the relational database schema you obtained in question~ \ref{ERtoREL} of Problem~ \ref{probERtoREL}, write the \texttt{SQL} implementation of that database.
367 Then, using MySQL Workbench, use the "Reverse Engineering" function to obtain a E.E.R. diagram of your database, and compare it with the U.M.L. diagram you draw in question~ \ref{ERtoUML} of Problem~ \ref{probERtoREL}.
368 Apart from the difference inherent to the nature of the diagram (i.e., U.M.L. Vs E.E.R.), how are they the same? How do they differ? Is the automated tool as efficient and accurate as you are?
369
370
371 Solution +.#
372 ~ <!--
373 \inputminted{sql}{include/sol.sql}
374 \includegraphics{include/mysql_workbench_drawing-crop}
375 -->
376
377 <!--
378 ~~~include
379 include/sol.sql
380 ~~~
381
382 -->
383
384 **Code à inclure ici**
385
386 ![](include/mysql_workbench_drawing-crop.pdf)
387
388 %%% 07
389
390
391 Exercise +.#
392 ~ What are the technologies that makes it possible for a Java application to communicate with a DBMS?
393
394
395 Solution +.#
396 ~ API + driver
397
398
399 Exercise +.#
400 ~ What JDBC method do you call to get a connection to a database?
401
402 Solution +.#
403 ~ DriverManager.getConnection()
404
405
406 Exercise +.#
407 ~ Briefly explain what the \texttt{next()} method from the \texttt{ResultSet} class does, and what is its return type.
408
409 Solution +.#
410 ~ It checks if there is data to read, and if move the cursor reads it.
411 It returns a Boolean.
412
413
414 Exercise +.#
415 ~ How do you submit a `SELECT` statement to the DBMS?
416
417
418 Solution +.#
419 ~ Using
420
421 ~~~{.java}
422 .executeQuery(strSelect)
423 ~~~
424
425 Exercise +.#
426 ~ Where is a ResultSet object's cursor initially pointing? How do you move the cursor forward in the result set?
427
428
429 Solution +.#
430 ~ Before the first line.
431
432 ~~~{.java}
433 next()
434 ~~~
435
436 method
437
438 Exercise +.#
439 ~ Give three navigation methods provided by `ResultSet`.
440
441
442 Solution +.#
443 ~ `first()`
444 `last()`
445 `next()`
446 `previous()`
447 `relative(rows)`
448 `absolute(row)` method.
449
450
451 Exercise +.#
452 ~ Explain this JDBC URL format:
453
454 ~~~{.java}
455 jdbc:mysql://localhost:3306/HW_NewDB?createDatabaseIfNotExist=true&useSSL=true
456 ~~~
457
458 Solution +.#
459 ~ Connect to localhost:3306 and create a new database if needed, and use secure connection.
460
461
462 Exercise +.#
463 ~ In what class is the `getColumnName()} method?
464
465
466 Solution +.#
467 ~ ResultSetMetaData
468
469
470 Exercise +.#
471 ~ What is a prepared statement?
472
473
474 Solution +.#
475 ~ A prepared statement is a feature used to execute the same (or similar) SQL statements repeatedly with high efficiency.
476
477
478 Exercise +.#
479 ~ In the code below, there are \(5\) errors between line \(11\) and line \(30\). They are \emph{not} subtle Java errors (like misspelling a key word) and do not come from the DBMS (so you should assume that the password is correct, that the database exists, etc.). For each error, highlight it precisely and give a short explanation.
480
481 ~~~{.java}
482 import java.sql.*;
483
484 public class MyProg{
485 public static void main(String[] args) {
486 try (
487 Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/"
488 +"HW_TestDB?user=testuser&password=password");
489 Statement stmt = conn.createStatement();
490 ) {
491
492 /* Errors after this point.*/
493
494 String strSelect = "SELECT title WHERE qty > 40 FROM disks;";
495 ResultSet rset = stmt.executeUpdate(strSelect);
496
497 System.out.println("The records selected are: (listed last first):");
498 rset.last();
499
500 while(rset.previous()) {
501 String title = rset.getDouble("title");
502 System.out.println(title + "\n");
503 }
504
505 String sss = "SELECT title FROM disks WHERE Price <= ?";
506 PreparedStatement ps = conn.prepareStatement(sss);
507 ResultSet result = ps.executeQuery();
508
509 conn.close();
510
511 /* Errors before this point.*/
512
513 } catch(SQLException ex) {
514 ex.printStackTrace();
515 }
516 }
517 }
518 ~~~
519
520 %
521 %METADATA
522 %
523 %ResultSet is array, other?
524 %
525 %Multiple queries
526 %
527 %qet datatype
528 %
529 %prepared statemernt.
530 %
531 %http://tutorials.jenkov.com/jdbc/resultset.html
532
533
534
535 48 This part will mainly hands on, and ask you to read code. This part will mainly hands on, and ask you to read code.
536 49 It is important that you learn how to get a working environment for a new technology quickly, for your understanding of this lecture, for the exam, and as a CS major. It is important that you learn how to get a working environment for a new technology quickly, for your understanding of this lecture, for the exam, and as a CS major.
537 50 I'll assume that you will have successfully completed those tasks , so don't wait and let me know if you had difficulties solving them. I'll assume that you will have successfully completed those tasks , so don't wait and let me know if you had difficulties solving them.
File notes/00_sum.md changed (mode: 100644) (index 53b9c2f..629165a)
... ... EXIT;
1931 1931
1932 1932 Problem-.+.#creatingSchema Problem-.+.#creatingSchema
1933 1933
1934 *This exercise assume you successfully completed @installation.*
1934 *This exercise assume you successfully completed @problem:installation.*
1935 1935
1936 1936 #. Connect to your MySQL DBMS as `testuser`: #. Connect to your MySQL DBMS as `testuser`:
1937 1937 - **In windows**, open a command prompt (search for "cmd") and type - **In windows**, open a command prompt (search for "cmd") and type
 
... ... Since there are small variations from one implementation to the other, it's bett
2021 2021
2022 2022 ### Creating and Using a Table ### Creating and Using a Table
2023 2023
2024 *This exercise, and the following ones, assume you successfully completed @installation.*
2024 *This exercise, and the following ones, assume you successfully completed @problem:installation.*
2025 2025
2026 2026 Log in as `testuser` and create a database `HW_2Q3`. Log in as `testuser` and create a database `HW_2Q3`.
2027 2027
 
... ... and to examine carefully the message printed. You should read
2095 2095 +------------+-------------+------+-----+---------+-------+ +------------+-------------+------+-----+---------+-------+
2096 2096 ~~~ ~~~
2097 2097
2098 If you believe there is a mistake, you can erase ("drop") the \emph{table} (not the whole database, as we did in @creatingSchema) using
2098 If you believe there is a mistake, you can erase ("drop") the \emph{table} (not the whole database, as we did in @problem:creatingSchema) using
2099 2099
2100 2100 ~~~{.sqlmysql} ~~~{.sqlmysql}
2101 2101 DROP TABLE ADDRESS; DROP TABLE ADDRESS;
 
... ... Populate them with some data.
2286 2286 ## Solution to Selected Problems ## Solution to Selected Problems
2287 2287
2288 2288 ### ###
2289 Solution for @#repetition
2289 Solution for @problem:repetition
2290 2290 ~ ~
2291 2291
2292 2292 ~~~{.sqlmysql} ~~~{.sqlmysql}
 
... ... Exercise +.#
3219 3219 #. If \(B\) is the only key, is \(B \to \{A, C, D\}, A \to \{C, D\}, \{A, C\} \to D\) a 3NF? List the nonprime attributes and justify. #. If \(B\) is the only key, is \(B \to \{A, C, D\}, A \to \{C, D\}, \{A, C\} \to D\) a 3NF? List the nonprime attributes and justify.
3220 3220
3221 3221
3222 Exercise +.#
3223 ~ Consider the relation \(R(A, B, C, D, E)\) and the functional dependencies \( \{A, B\} \to C, B \to D, C \to E\). Answer the following:
3224
3225 #. \(A\) by itself is not a primary key, but what is the only key that contains \(A\)?
3226 #. List the non-prime attributes.
3227 #. This relation is not in 2NF: what transformation can you operate to obtain a 2NF?
3228 #. One of the relation you obtained at the previous step is likely not to be in 3NF. Can you normalize it? If yes, how?
3229
3230 Exercise +.#
3231 ~ What are the two different categories of U.M.L. diagram?
3232
3233 Exercise +.#
3234 ~ Can a `C++` developer working on Linux and a `Java` developer working on MacOS use the same class diagram as a basis to write their programs?
3235 Justify your answer.
3236
3237 Exercise +.#
3238 ~ What kind of diagram should we use if we want to …
3239
3240 #. describe the functional behavior of the system as seen by the user?
3241 #. capture the flow of messages in a software?
3242 #. represent the workflow of actions of an user?
3243
3244 Exercise +.#
3245 ~ Name two reasons why one would want to use a U.M.L. class diagram over an E.-R. diagram to represent a conceptual schema.
3246
3247 Exercise +.#
3248 ~ Consider the following diagram:
3249
3250 \begin{tikzpicture}[scale = 0.8]
3251 \begin{class}[text width=7cm]{Flight}{0,0}
3252 \attribute{flightNumber : Integer}
3253 \attribute{departureTime : Date}
3254 \attribute{flightDuration : Minutes}
3255 \attribute{departingAirport : String}
3256 \attribute{arrivingAirport : String}
3257 \operation{delayFlight(numberOfMinutes : Minutes)}
3258 \operation{getArrivalTime( ) : Date}
3259 \end{class}
3260 \begin{class}{Plane}{11, -0.8}
3261 \attribute{airPlaneType : String}
3262 \attribute{maximumSpeed : MPH}
3263 \attribute{maximumDistance : Miles}
3264 \attribute{tailID : String}
3265 \end{class}
3266 \association{Plane}{}{0..1}{Flight}{0..*}{}
3267 \end{tikzpicture}
3268
3269 Give the number of attributes for both classes, and suggest two operations for the class that doesn't have any. Discuss the multiplicities: why did the designer picked those values?
3270
3271 Exercise +.#
3272 ~ Briefly explain the difference between an aggregation and a composition association.
3273
3274
3275 Exercise +.#
3276 ~ How is generalization (or inheritance) represented in a U.M.L. class diagram?
3277 Why is such a concept useful?
3278
3279 Exercise +.#
3280 ~ Convert the following E.R. diagram into a U.M.L. class diagram:
3281
3282 \begin{tikzpicture}[node distance=8em]
3283 \node[entity] (person) {PILOT};
3284 \node[attribute] (pid) [left of=person] {\key{ID}} edge (person);
3285 \node[attribute] (name) [above left of=person] {Name} edge (person);
3286 \node[attribute] (phone) [above of=person] {Experience} edge (person);
3287
3288 \node[relationship] (drives) [below of=person] {ASSIGNED\_TO} edge node[right, pos=0.1] {$N$} (person);
3289 \node[entity] (plane) [below of=drives] {PLANE} edge [total] node[right, pos=0.7] {$1$} (drives);
3290 \node[attribute] (make) [left of=plane] {\key{TailID}} edge (plane);
3291 \node[attribute] (maxS) [below left of =plane] {MaxSpeed} edge (plane);
3292 \node[attribute] (airPlaneType) [below of = plane] {AirPlaneType} edge (plane);
3293 \end{tikzpicture}
3294
3222 3295 ## Solution to Exercises ## Solution to Exercises
3223 3296
3224 3297 Solution +.# Solution +.#
 
... ... Solution +.#
3376 3449
3377 3450 2. No. \(A\), \(B\) and \(D\) are non prime, \(B \to \{A,C\} \to D\) breaks the 3NF. 2. No. \(A\), \(B\) and \(D\) are non prime, \(B \to \{A,C\} \to D\) breaks the 3NF.
3378 3451
3452 Solution +.#
3453
3454 \(\{A, B\}\),
3455
3456 \(C, D, E\),
3457
3458 \(R_1(A, B, C, E)\) and \(R_2(B, D)\)
3459
3460 \(R_1(A, B, C)\), \(R_2(C, E)\) and \(R_3(B, D)\)
3461
3462 Solution +.#
3463 ~ Behaviour and structure
3464
3465 Solution +.#
3466 ~ Yes, U.M.L. diagram is language-independent and platform-independent.
3467
3468 Solution +.#
3469 ~ 1. Use-case
3470 2. Sequence diagram
3471 3. Activity diagram
3472
3473 Solution +.#
3474 ~ To use direction for association, to have a common language with someone less knowledgeable of other diagrammatic notations.
3475 For the concept of integration.
3476
3477
3478 Solution +.#
3479 ~ \(5\) and \(4\).
3480
3481 getLastFlightNumber() : Integer
3482
3483 stMaximumSpeed(MPH) : void
3484
3485 A flight could be assigned to no plane, and a plane could not be assigned to a flight.
3486
3487 A plane can be assigned to multiple (or no) flights, but a flight must have at most one plane (and could have none).
3488
3489 Solution +.#
3490 ~ Aggregation: associated class can have an existence of its own.
3491
3492 Composition association: class doesn't exist without the association.
3493
3494 Solution +.#
3495 ~ \tikz{\draw[>=open triangle 60,->] (0,0) to (1,0);}
3496 Because it avoids redundancy.
3497
3379 3498
3380 3499 ## Problems ## Problems
3381 3500
3382 Problem +.#Movie
3501 Problem +.#movie
3383 3502
3384 3503 Consider the ER schema for the MOVIES database: Consider the ER schema for the MOVIES database:
3385 3504
 
... ... Problem +.#
3448 3567
3449 3568 Apply the ER-to-Relation mapping to your ER diagram from the previous problem. Apply the ER-to-Relation mapping to your ER diagram from the previous problem.
3450 3569
3451 Problem +.#CarSale
3570 Problem +.#carsale
3452 3571
3453 3572 Consider the following relation, and its functional dependencies: Consider the following relation, and its functional dependencies:
3454 3573
 
... ... Email | → | \{Fname, Lname, Phone\}
3507 3626 Normalize the relations to 2NF and 3NF. Show all relations at each stage (2NF and 3NF) of the normalization process. Normalize the relations to 2NF and 3NF. Show all relations at each stage (2NF and 3NF) of the normalization process.
3508 3627
3509 3628
3510 Problem +.#Book
3629 Problem +.#book
3511 3630
3512 3631 Consider the following relation for published books: Consider the following relation for published books:
3513 3632
 
... ... Author\_name | → | Author\_affil
3526 3645 - This relation is not in second normal form: explain why and normalize it. - This relation is not in second normal form: explain why and normalize it.
3527 3646 - Is the relations you obtained at the previous step in third normal form? Explain why, and normalize them if needed. - Is the relations you obtained at the previous step in third normal form? Explain why, and normalize them if needed.
3528 3647
3648 Problem +.#MYSQLW
3649
3650 Consider the following E.R. schema for the CAR\_INFO database:
3651
3652 \begin{tikzpicture}[node distance=8em]
3653 \node[entity] (person) {PERSON};
3654 \node[attribute] (pid) [left of=person] {\key{ID}} edge (person);
3655 \node[attribute] (name) [above left of=person] {Name} edge (person);
3656 \node[multi attribute] (phone) [above of=person] {Phone} edge (person);
3657 \node[attribute] (address) [above right of=person] {Address} edge (person);
3658 \node[attribute] (street) [above right of=address] {Street} edge (address);
3659 \node[attribute] (city) [right of=address] {City} edge (address);
3660 %\node[derived attribute] (age) [right of=person] {Age} edge (person);
3661
3662 \node[relationship] (drives) [below right of=person] {DRIVES} edge node[above, pos=0.1] {$1$} (person);
3663 \node[entity] (car) [below left of=drives] {CAR} edge node[above, pos=0.7] {$1$} (drives);
3664 \node[attribute] (make) [left of=car] {Make} edge (car);
3665 \node[attribute] (year) [below left of =car] {Year} edge (car);
3666 \node[attribute] (brand) [below of =car] {Brand} edge (car);
3667
3668 \node[relationship] (seats) [below left of=person] {SEATS\_IN} edge node[above, pos=0.1] {$N$} (person);
3669 \draw (seats) edge node[above, pos=0.3] {$1$} (car);
3670 \node[attribute] (position) [left of=seats] {Position} edge (seats);
3671
3672 \node[ident relationship] (insured) [right of=car] {INSURED} edge node[above, pos=0.3] {$1$} (car);
3673 \node[weak entity] (insurance) [right = 1cm of insured] {CAR\_INSURANCE} edge[total] node[above, pos=0.7] {$N$} (insured);
3674 \node[attribute] (amount) [above of =insurance] {Covered Amount} edge (insurance);
3675 \node[attribute] (policy) [above right of =insurance] {Policy Number} edge (insurance);
3676 \node[attribute] (company) [below right of =insurance] {Company Name} edge (insurance);
3677 \end{tikzpicture}
3678
3679 Note that a car can have at most one driver, \(N\) passengers, \(N\) insurances, and that car insurances exist only if they are "tied up" to a car (i.e., they are weak entities, and their identifying relationship is called "Insured").
3680
3681 1. Find the key attribute for "Car", and the partial key for "Car Insurance". If you can't think of any, add a dummy attribute and make it be the key.
3682 2. Convert that E.-R. diagram to a relational database schema.
3683 3. Convert the E.-R. diagram to a U.M.L. class diagram. Comparing Figure 7.16 with Figure 7.2 from your textbook should guide you.
3684
3685
3686 Problem +.#
3687
3688 In this exercise, we will install and explore the basic functionalities of MySQL Workbench, which is a cross-platform, open-source, and free graphical interface for database design.
3689
3690 1. Install MySQL Workbench: use your package manager, or download the binaries from \url{https://dev.mysql.com/downloads/workbench/}.
3691 2. Once installed, execute the software. Under the panel "MySQL Connections", you should see your local installation listed as "Local instance 3306". Click on the top-right corner of that box, and then on "Edit Connections". Alternatively, click on "Database", on "Manage Connections", and then on "Local instance 3306".
3692 3. Check that all the parameters are correct. Normally, you only have to change the name of the user to "testuser", and leave the rest as it is. Click on "Test the connection", and enter your password (which should be "password") when prompted. If you receive a warning about "Incompatible/nonstandard server version or connection protocol detected", click on "Continue anyway".
3693 4. Now, click on the box "Local instance 3306", and enter your password. A new tab appears, you can see the list of schemas in the bottom part of the left panel.
3694 5. Click on "Database", and then on "Reverse Engineering" (or hit \texttt{ctrl} + \texttt{r}), click on "next", enter your password, and click on "next". You should see the list of the schemas stored in your database. Select one (any one, we are just exploring the functionalities at that point), click on "next", and then click on "execute", "next", and "close".
3695 6. You're back on the previous view, but you should now see "E.E.R. diagram" on the top of the middle panel. Click on "E.E.R. diagram" twice, scroll down if needed, and you should see the E.E.R. diagram.
3696 7. This diagram isn't exaclty an E.-R. diagram, and it's not a U.M.L. diagram either. Yet, you should still be able to understand parts of it, and should try to modify it. Make some relations mandatory, change their name, add an attribute, change the name of another, insert a couple of elements in an entity, add a row in a table, etc. Make sure you understand the meaning of the lines between the entities.
3697 8. Once you're done, try to "Forward Engineer" by hitting "Ctrl" + "G". Click on "next" twice, enter your password, click on lick on "next" once more, and you should see the \texttt{SQL} code needed to produce the table you just designed using the graphical tool.
3698
3699
3700 Problem +.#ReverseEng
3701
3702 *This problem requires you to have successfully completed @probleme:MYSQLW and @problem:ERtoREL.*
3703
3704 Using the relational database schema you obtained in question~\ref{ERtoREL} of @problem:ERtoREL, write the `SQL` implementation of that database.
3705 Then, using MySQL Workbench, use the "Reverse Engineering" function to obtain a E.E.R. diagram of your database, and compare it with the U.M.L. diagram you draw in question~ \ref{ERtoUML} of @problem:ERtoREL.
3706 Apart from the difference inherent to the nature of the diagram (i.e., U.M.L. Vs E.E.R.), how are they the same? How do they differ? Is the automated tool as efficient and accurate as you are?
3707
3529 3708 ## Solution to Selected Problems ## Solution to Selected Problems
3530 3709
3531 ### Solution to the @Movie
3710 ### Solution to the @problem:movie
3532 3711
3533 3712 #. true #. true
3534 3713 #. true #. true
 
... ... Author\_name | → | Author\_affil
3544 3723 #. true #. true
3545 3724 #. false #. false
3546 3725
3547 ### Solution to @CarSale
3726 ### Solution to @problem:carsale
3548 3727
3549 3728 This relation satisfies 1NF but not 2NF (Car\_no → Date\_sold and Salesman\_no → Commission so these two attributes are not fully functional dependent on the primary key) and not 3NF. This relation satisfies 1NF but not 2NF (Car\_no → Date\_sold and Salesman\_no → Commission so these two attributes are not fully functional dependent on the primary key) and not 3NF.
3550 3729
 
... ... Car\_Sale2(Car\_no, Salesman\_no)\\
3564 3743 Car\_Sale3(Salesman\_no,Commission) Car\_Sale3(Salesman\_no,Commission)
3565 3744 \end{tabular} \end{tabular}
3566 3745
3567 ### Solution to @Bike
3746 ### Solution to @problem:bike
3568 3747
3569 3748 - -
3570 3749 #. \{ Manufacturer, Serial\_no \} → \{ Model, Batch, Wheel\_size, Retailer\} #. \{ Manufacturer, Serial\_no \} → \{ Model, Batch, Wheel\_size, Retailer\}
 
... ... Car\_Sale3(Salesman\_no,Commission)
3575 3754 - \{Manufacturer, Serial\_no \} - \{Manufacturer, Serial\_no \}
3576 3755 - If every attribute is atomic, it is in second nf. \{ Manufacturer, Serial\_no \} → Batch →Model breaks the 3NF. - If every attribute is atomic, it is in second nf. \{ Manufacturer, Serial\_no \} → Batch →Model breaks the 3NF.
3577 3756
3578 ### Solution to @Book
3757 ### Solution to @problem:book
3579 3758
3580 3759 - \{Book Title, Author Name\} - \{Book Title, Author Name\}
3581 3760 - If an attribute is composite or multi-valued. - If an attribute is composite or multi-valued.
 
... ... We can normalize it as
3585 3764 - Because of \{Book title\} → \{ Book\_type\} → \{ List\_price\}\\ - Because of \{Book title\} → \{ Book\_type\} → \{ List\_price\}\\
3586 3765 (Book Title, Publisher, Book Type) and (Book Type, List Price), (Author Name, Author Affiliation), (Author Name, Book Title). (Book Title, Publisher, Book Type) and (Book Type, List Price), (Author Name, Author Affiliation), (Author Name, Book Title).
3587 3766
3767 Solution for @probleme:MYSQLW
3768 ~ For "Car", we need to create an attribute, like "vin".
3769 For "Car Insurance", "Policy Number" is perfect.
3770
3771 \colorlet{lightgray}{gray!20}
3772
3773 \begin{tikzpicture}[relation/.style={rectangle split, rectangle split parts=#1, rectangle split part align=base, draw, anchor=center, align=center, text height=3mm, text centered}]\hspace*{-0.3cm}
3774
3775 % RELATIONS
3776
3777 \node (phonetitle) {**PHONE**};
3778
3779 \node [relation=2, rectangle split horizontal, rectangle split part fill={lightgray!50}, anchor=north west, below=0.6cm of phonetitle.west, anchor=west] (phone)
3780 {\underline{id}%
3781 \nodepart{two} \underline{number}
3782 };
3783
3784 \node [below=1.3cm of phone.west, anchor=west] (persontitle) {**PERSON**};
3785
3786 \node [relation=6, rectangle split horizontal, rectangle split part fill={lightgray!50}, below=0.6cm of persontitle.west, anchor=west] (person)
3787 {\underline{id}%
3788 \nodepart{two} Name
3789 \nodepart{three} Street
3790 \nodepart{four} City
3791 \nodepart{five} Seat
3792 \nodepart{six}{Position}
3793 };
3794
3795 \node [below=1.1cm of person.west, anchor=west] (cartitle) {**CAR**};
3796
3797 \node [relation=5, rectangle split horizontal, rectangle split part fill={lightgray!50}, anchor=north west, below=0.6cm of cartitle.west, anchor=west] (car)
3798 {\underline{Vin}%
3799 \nodepart{two} Make
3800 \nodepart{three} Year
3801 \nodepart{four} Brand
3802 \nodepart{five} Driver
3803 };
3804
3805 \node [below=1.4cm of car.west, anchor=west] (carinsurancetitle) {**CAR INSURANCE**};
3806
3807 \node [relation=4, rectangle split horizontal, rectangle split part fill={lightgray!50}, anchor=north west, below=0.6cm of carinsurancetitle.west, anchor=west] (carinsurance)
3808 {\underline{Policy Number}%
3809 \nodepart{two} Covered Amount
3810 \nodepart{three} Company Name
3811 \nodepart{four} Insured Car
3812 };
3813
3814 % FOREIGN KEYS
3815
3816 \draw[-latex] (phone.one south) -- ++(0,-0.2) --++(7,0) --++(0, -2) -| ($(person.one south) + (0.2,0)$);
3817 %\draw[-latex] (person.five south) -- ++(0,-0.2) --++(3,0) --++(0, -2) -| ($(car.one south) + (-0.2,0)$);
3818 \draw[-latex] (carinsurance.four south) -- ++(0,-0.2) --++(2,0) --++(0, 1.75) -| ($(car.one south) + (0.1,0)$);
3819 \draw[-latex] (car.five south) -- ++(0,-0.2) --++(2,0) --++(0, 1.5) -| ($(person.one south) + (-0.1,0)$);
3820 \end{tikzpicture}
3821
3822
3823 \begin{tikzpicture}[scale = 0.8]
3824 \node (person) at (0,0){\begin{tabular}{| r l |}
3825 \hline
3826 \multicolumn{2}{| c |}{**Person**}\\
3827 \hline
3828 id &: String\\
3829 name &: String\\
3830 address &: Street\\
3831 & City\\
3832 \hline
3833 getAge()&: Int\\
3834 \hline
3835 \end{tabular}
3836 };
3837 \node (phone) at (8, 1){\begin{tabular}{| r l |}
3838 \hline
3839 \multicolumn{2}{| c |}{**Phone**}\\
3840 \hline
3841 number &: String\\
3842 \hline
3843 \end{tabular}
3844 };
3845 \draw[open diamond-] (person) -- node[above, pos=0.1]{\(0..\star\)} node[above, pos=0.9]{\(1..1\)} (phone);
3846 \node (car) at (8, -3){\begin{tabular}{| r l |}
3847 \hline
3848 \multicolumn{2}{| c |}{**Car**}\\
3849 \hline
3850 vin &: String\\
3851 make &: String\\
3852 year &: Year\\
3853 brand &: String\\
3854 \hline
3855 \end{tabular}
3856 };
3857 \draw[-] ($(person)+(2.5,-0.5)$) -- node[above, pos=0.1]{\(0..1\)} node[above, pos=0.5]{drives} node[above, pos=0.9]{\(0..1\)} (car);
3858 %\draw[-] (person) -- node[below, pos=0.1]{\(0..1\)} node[below, pos=0.9]{\(0..4\)} ($(car)+(-2.5, 0.5)$);
3859 \node (seat) at (3.5, -5){\begin{tabular}{| r l |}
3860 \hline
3861 \multicolumn{2}{| c |}{**Seats In**}\\
3862 \hline
3863 position &: String\\
3864 \hline
3865 \end{tabular}
3866 };
3867 \draw[dashed] (seat) -- (3.5, -1.6);
3868
3869 \node (insu) at (14.3, -2){\begin{tabular}{| r l |}
3870 \hline
3871 \multicolumn{2}{| c |}{**Car Insurance**}\\
3872 \hline
3873 policy number &: String\\
3874 covered amount &: int\\
3875 compagny name &: String\\
3876 \hline
3877 \end{tabular}
3878 };
3879
3880 \draw[diamond -] (car) -- node[above, pos=0.1]{\(0..\star\)} node[above, pos=0.9]{\(1\)} (insu);
3881 \end{tikzpicture}
3882
3883
3884 Solution to @problem:ReverseEng
3885 ~ <!--
3886 \inputminted{sql}{include/sol.sql}
3887 \includegraphics{include/mysql_workbench_drawing-crop}
3888 -->
3889
3890 <!--
3891 ~~~include
3892 include/sol.sql
3893 ~~~
3894
3895 -->
3896
3897 **Code à inclure ici**
3898
3899 ![](include/mysql_workbench_drawing-crop.pdf)
3900
3588 3901 # Databases Applications # Databases Applications
3589 3902
3590 3903 **Sources:** **Sources:**
 
... ... You can pass options when creating Statement objects to be able to read it both
3848 4161
3849 4162 **COPY HOMEWORK HERE** **COPY HOMEWORK HERE**
3850 4163
4164 ## Exercises
4165
4166 Exercise +.#
4167 ~ What are the technologies that makes it possible for a Java application to communicate with a DBMS?
4168
4169 Exercise +.#
4170 ~ What JDBC method do you call to get a connection to a database?
4171
4172
4173 Exercise +.#
4174 ~ Briefly explain what the `next()` method from the `ResultSet` class does, and give its return type.
4175
4176 Exercise +.#
4177 ~ How do you submit a `SELECT` statement to the DBMS?
4178
4179 Exercise +.#
4180 ~ Where is a `ResultSet` object's cursor initially pointing? How do you move the cursor forward in the result set?
4181
4182 Exercise +.#
4183 ~ Give three navigation methods provided by `ResultSet`.
4184
4185 Exercise +.#
4186 ~ Explain this JDBC URL format:
4187
4188 ~~~{.java}
4189 jdbc:mysql://localhost:3306/HW_NewDB?createDatabaseIfNotExist=true&useSSL=true
4190 ~~~
4191
4192 Exercise +.#
4193 ~ In what class is the `getColumnName()} method?
4194
4195 Exercise +.#
4196 ~ What is a prepared statement?
4197
4198
4199
4200 Exercise +.#
4201 ~ In the code below, there are \(5\) errors between line \(11\) and line \(30\). They are \emph{not} subtle Java errors (like misspelling a key word) and do not come from the DBMS (so you should assume that the password is correct, that the database exists, etc.). For each error, highlight it precisely and give a short explanation.
4202
4203 ~~~{.java}
4204 import java.sql.*;
4205
4206 public class MyProg{
4207 public static void main(String[] args) {
4208 try (
4209 Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/"
4210 +"HW_TestDB?user=testuser&password=password");
4211 Statement stmt = conn.createStatement();
4212 ) {
4213
4214 /* Errors after this point.*/
4215
4216 String strSelect = "SELECT title WHERE qty > 40 FROM disks;";
4217 ResultSet rset = stmt.executeUpdate(strSelect);
4218
4219 System.out.println("The records selected are: (listed last first):");
4220 rset.last();
4221
4222 while(rset.previous()) {
4223 String title = rset.getDouble("title");
4224 System.out.println(title + "\n");
4225 }
4226
4227 String sss = "SELECT title FROM disks WHERE Price <= ?";
4228 PreparedStatement ps = conn.prepareStatement(sss);
4229 ResultSet result = ps.executeQuery();
4230
4231 conn.close();
4232
4233 /* Errors before this point.*/
4234
4235 } catch(SQLException ex) {
4236 ex.printStackTrace();
4237 }
4238 }
4239 }
4240 ~~~
4241
4242 ## Solution to Exercises
4243
4244
4245
4246 Solution +.#
4247 ~ API + driver
4248
4249
4250
4251
4252 Solution +.#
4253 ~ DriverManager.getConnection()
4254
4255 Solution +.#
4256 ~ It checks if there is data to read, and if move the cursor reads it.
4257 It returns a Boolean.
4258
4259
4260 Solution +.#
4261 ~ Using
4262
4263 ~~~{.java}
4264 .executeQuery(strSelect)
4265 ~~~
4266
4267 Solution +.#
4268 ~ Before the first line. Using the `next` method.
4269
4270 Solution +.#
4271 ~ `first()`
4272 `last()`
4273 `next()`
4274 `previous()`
4275 `relative(rows)`
4276 `absolute(row)` method.
4277
4278 Solution +.#
4279 ~ Connect to localhost:3306 and create a new database if needed, and use secure connection.
4280
4281 Solution +.#
4282 ~ ResultSetMetaData
4283
4284 Solution +.#
4285 ~ A prepared statement is a feature used to execute the same (or similar) SQL statements repeatedly with high efficiency.
4286
4287 Solution +.#
4288 List errors in program TO DO.
4289
4290 <!--
4291 %
4292 %METADATA
4293 %
4294 %ResultSet is array, other?
4295 %
4296 %Multiple queries
4297 %
4298 %qet datatype
4299 %
4300 %prepared statemernt.
4301 %
4302 %http://tutorials.jenkov.com/jdbc/resultset.html
4303 -->
4304
4305
3851 4306 --- ---
3852 4307
3853 4308 # A Bit About Security # A Bit About Security
Hints:
Before first commit, do not forget to setup your git environment:
git config --global user.name "your_name_here"
git config --global user.email "your@email_here"

Clone this repository using HTTP(S):
git clone https://rocketgit.com/user/caubert/CSCI_3410

Clone this repository using ssh (do not forget to upload a key first):
git clone ssh://rocketgit@ssh.rocketgit.com/user/caubert/CSCI_3410

Clone this repository using git:
git clone git://git.rocketgit.com/user/caubert/CSCI_3410

You are allowed to anonymously push to this repository.
This means that your pushed commits will automatically be transformed into a merge request:
... clone the repository ...
... make some changes and some commits ...
git push origin main