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Material for Database Class.
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Adding second quiz, and fixing some exercises and problems in Chapter 3. 062c9b46fad52848efbf61e08c91103c0bae4127 aubert@math.cnrs.fr 2019-02-06 20:04:16
Clarification on SQL constraints. 70e26a02aa344cc1bf009a089623be6baac79ba7 aubert@math.cnrs.fr 2019-01-29 22:46:26
Adding some minor SQL remarks + code for HW_FACULTY. 1d1b74302d29fb63c3c2bacca30533283f720997 aubert@math.cnrs.fr 2019-01-25 17:24:16
fixing small typo. 0feeb8df61e05d6d0990120628303cf31108f100 aubert@math.cnrs.fr 2019-01-22 18:23:34
Quick fix + adding macOS install instructions. ea3063e4e9225c8ce66838c8bfddb9a34aadacf8 aubert@math.cnrs.fr 2019-01-16 15:59:38
Fixing a few typos and adding a drawing. b335800d4129c8e29763a6c1d564243d485fa51b aubert@math.cnrs.fr 2019-01-15 19:03:38
Fixing first homework 3eeb05a78235274a330c780f4f26b5fed1a01aef aubert@math.cnrs.fr 2019-01-08 19:50:29
Added content of various exam, fixed intro, added references, solutions, fixed types. a8e9d2d4856133d68d882403cde42dfcc2f5cc69 aubert@math.cnrs.fr 2019-01-07 16:47:02
Cleaning files and makefile 7605a6530505ad69042413dd995d77f1814c2f30 au 2018-12-24 14:25:31
Fixed margin for PDF, added a couple of SVG images, fixed some problems, added some code. eb83d9f07d738df7ab2515b768d6165a3b7e5ca3 au 2018-12-24 02:28:36
Working on rel_mod for Prof_Department_Extended. 2b1eff83797fbda620189f014043d648c884e887 au 2018-12-23 22:38:07
Working on FD and various figures. 8fd7f8322e70ae252596aa9cb88918ac40d5aa84 au 2018-12-23 20:25:19
Added first drawing for fd. 2a0e4fc716d91c23c81346a0e3b568f7132284c9 au 2018-12-23 05:23:29
Cleaned latex code. 1cf04e85915d24fc0208b407eb0166803b2369cf au 2018-12-23 04:27:41
Working on drawing for functional dependencies. 7dc167021630c00be25881877c0921adbc87f482 au 2018-12-23 04:20:33
Working on style for functional dependencies graph. 029c32395ba1110ad2af980e248848e0877040d7 au 2018-12-23 00:17:54
Working on template for FD. 091bb061b6fea06f440e97a4c9ac0f69b4ea1392 au 2018-12-22 20:57:00
Started to work on Functional Dep. 2123fbafc3b8258184ad745d8f23521a3f477d0e au 2018-12-22 18:53:20
Fixing a couple of problem, adding some more correct figures. ef44b65f45fba2bd9a653b639287d872b9f7471d au 2018-12-22 04:27:34
Fixing two figures, and renaming them. 71f4ab9c4090e97da19089f2316e87a4ebe838d6 au 2018-12-22 02:37:15
Commit 062c9b46fad52848efbf61e08c91103c0bae4127 - Adding second quiz, and fixing some exercises and problems in Chapter 3.
Author: aubert@math.cnrs.fr
Author date (UTC): 2019-02-06 20:04
Committer name: aubert@math.cnrs.fr
Committer date (UTC): 2019-02-06 20:04
Parent(s): 70e26a02aa344cc1bf009a089623be6baac79ba7
Signer:
Signing key:
Signing status: N
Tree: 501ca6084fdf9e8b65109ab4bd50b2dfa723c727
File Lines added Lines deleted
notes/lectures_notes.md 103 41
File notes/lectures_notes.md changed (mode: 100644) (index aa3bffc..8791dee)
... ... Exercise +.#
729 729
730 730 : What, if any, is the difference between a superkey, a key, and a primary key? : What, if any, is the difference between a superkey, a key, and a primary key?
731 731
732 Exercise +.#
733
734 : Name the two kind of integrities that must be respected by the tuples in a relation.
735
732 736 Exercise +.#entityintegrity Exercise +.#entityintegrity
733 737
734 738 : What is entity integrity? Why is it useful? : What is entity integrity? Why is it useful?
 
... ... Exercise +.#
739 743
740 744 Exercise +.# Exercise +.#
741 745
746 : If in a relation $R_1$, an attribute $A_1$ is a foreign key referencing an attribute $A_2$ in a relation $R_2$, what does this implies about $A_2$?
747
748 Exercise +.#
749
742 750 : Give three examples of operations. : Give three examples of operations.
743 751
752 Exercise +.#
753 ~
754 Consider the following two relations:
755
756 COMPUTER(Owner, RAM, Year, Brand)
757 OS(Name, Version, Architecture)
758
759 For each, give a) The arity of the relation, b) A (preferably plausible) example of tuple to insert.
760
744 761 Exercise +.# Exercise +.#
745 762
746 763 : Define what is the domain constraint. : Define what is the domain constraint.
 
... ... Exercise +.#
782 799 #. `Insert <'XB-124', 'GPalmer', '02/04/2018'> into ASSIGNED-TO` #. `Insert <'XB-124', 'GPalmer', '02/04/2018'> into ASSIGNED-TO`
783 800 #. `Insert <'BTed, 'Bobby Ted', 'Senior'> and <'BTed', 'Bobby Ted Jr.', 'Junior'> into CONDUCTOR` #. `Insert <'BTed, 'Bobby Ted', 'Senior'> and <'BTed', 'Bobby Ted Jr.', 'Junior'> into CONDUCTOR`
784 801
802
803 Exercise +.#
804 ~ Consider the following relation schema and state:
805
806 <!-- Bug with table -->
807 **A** | **B** | **C** | **D** |
808 --- | --- | --- | --- |
809 2 | Blue | Austin | `true`|
810 1 | Yellow | Paris | `true` |
811 1 | Purple | Pisa | `false`|
812 2 | Yellow | Augusta | `true`|
813
814 Assuming that this is all the data we will ever have, discuss whenever $\{A, B, C, D\}$, $\{A, B\}$ and $\{B\}$ are superkeys and/or keys.
815
785 816 ## Solution to Exercises {-} ## Solution to Exercises {-}
786 817
787 818 Solution +.# Solution +.#
 
... ... The primary key is one of the candidate key, i.e., the key that was chosen.
812 843
813 844 Solution +.# Solution +.#
814 845
846 : Referential integrity and entity integrity.
847
848 Solution +.#
849
815 850 : Entity integrity ensures that each row of a table has a unique and non-null primary key value. It allows to make sure that every tuple is different from the others, and helps to "pick" elements in the database. : Entity integrity ensures that each row of a table has a unique and non-null primary key value. It allows to make sure that every tuple is different from the others, and helps to "pick" elements in the database.
816 851
817 852 Solution +.# Solution +.#
 
... ... Solution +.#
820 855
821 856 Solution +.# Solution +.#
822 857
858 : Then we know that $A_2$ is the primary key of $R_2$.
859
860 Solution +.#
861
823 862 : Reading from the database, performing `UPDATE`{.sqlmysql} or `DELETE`{.sqlmysql} operations. : Reading from the database, performing `UPDATE`{.sqlmysql} or `DELETE`{.sqlmysql} operations.
824 863
864 Solution +.#
865 ~
866
867 a) COMPUTER has for arity $4$, and OS has for arity $3$.
868 b) ("Linda McFather", 32, 2017, "Purism"), and ("Debian", "Stable", "amd64")
869
825 870 Solution +.# Solution +.#
826 871
827 872 : The requirement that each tuple must have for an attribute $A$ an atomic value from the domain dom($A$), or `NULL`{.sqlmysql}. : The requirement that each tuple must have for an attribute $A$ an atomic value from the domain dom($A$), or `NULL`{.sqlmysql}.
 
... ... Solution +.#
850 895 #. No, it violates the referential integrity constraint: `'XB-124` and `'GPalmer'` are not values in `TRAIN.Ref` and `CONDUCTOR.CompanyID`. #. No, it violates the referential integrity constraint: `'XB-124` and `'GPalmer'` are not values in `TRAIN.Ref` and `CONDUCTOR.CompanyID`.
851 896 #. No, it violates the key constraint: two tuples can't have the same value for the primary key. #. No, it violates the key constraint: two tuples can't have the same value for the primary key.
852 897
898 Solution +.#
899 ~
900
901 - $\{A, B, C, D\}$ is a superkey (the set of all the attributes is always a superkey), but not a superkey, as removing e.g. $D$ would still make it a superkey.
902 - $\{A, B\}$ is a superkey **and** a key, as neither $\{A\}$ nor $\{B\}$ are keys.
903 - $\{A\}$ is not a key, and not a superkey: multiple tuples have the value $1$.
904
853 905 ## Problems {-} ## Problems {-}
854 906
855 907 Problem (Finding candidate key in a CLASS relation) +.#candidatekeyinclass Problem (Finding candidate key in a CLASS relation) +.#candidatekeyinclass
 
... ... Type and domains are two different things in some implementations, cf. for insta
988 1040 The following commands are particularly useful: The following commands are particularly useful:
989 1041
990 1042 ~~~{.sqlmysql} ~~~{.sqlmysql}
991 SHOW SCHEMAS; -- List the schema
992 SHOW TABLES; -- List the tables in a schema
993 DESCRIBE <TableName>; -- Show the structure of a table
994 SELECT * FROM <TableName> -- List all the rows in a table
995 DROP TABLE <TableName>; -- "Drop" (erase) a table
996 DROP SCHEMA <SchemaName>; -- Drop a schema
1043 SHOW SCHEMAS; -- List the schemas.
1044 SHOW TABLES; -- List the tables in a schema.
1045 SHOW CREATE TABLE <TableName> -- Gives the command to "re-construct" TableName.
1046 DESCRIBE <TableName>; -- Show the structure of TableName.
1047 SELECT * FROM <TableName> -- List all the rows in TableName.
1048 DROP TABLE <TableName>; -- "Drop" (erase) TableName.
1049 DROP SCHEMA <SchemaName>; -- "Drop" (erase" SchemaName.
997 1050 SHOW WARNINGS; -- After a warning was issued, show the content of the warning. SHOW WARNINGS; -- After a warning was issued, show the content of the warning.
998 1051 ~~~ ~~~
999 1052
 
... ... For `DISTINCT`, `ALL` and `UNION`, cf. [@Textbook6, 4.3.4] or [@Textbook7, 6.3.
1502 1555 For `ORDER BY` , cf. [@Textbook6, 4.3.6] or [@Textbook7, 6.3.6]. For `ORDER BY` , cf. [@Textbook6, 4.3.6] or [@Textbook7, 6.3.6].
1503 1556 For aggregate functions, cf. [@Textbook6, 5.1.7] or [@Textbook7, 7.1.7]. For aggregate functions, cf. [@Textbook6, 5.1.7] or [@Textbook7, 7.1.7].
1504 1557
1558
1559 ### Transactions
1560
1561 We can save the current state, and start a series of transactions, with the command
1562
1563 ~~~{.sqlmysql}
1564 START TRANSACTION;
1565 ~~~
1566
1567 All the commands that follows are "virtually" executed: you can undo them all using
1568
1569 ~~~{.sqlmysql}
1570 ROLLBACK;
1571 ~~~
1572
1573 This puts you back in the state you were in before starting the transaction.
1574 If you want all the commands you typed in-between to be actually enforced, you can use the command
1575
1576 ~~~{.sqlmysql}
1577 COMMIT;
1578 ~~~
1579
1580 Nested transactions are technically possible, but they are counter-intuitive and should be avoided, cf. <https://www.sqlskills.com/blogs/paul/a-sql-server-dba-myth-a-day-2630-nested-transactions-are-real/>.
1581
1505 1582 ### DISTINCT / ALL ### DISTINCT / ALL
1506 1583
1507 1584 The result of a `SELECT` query, for instance, is a table, and SQL treats tables as multi-set, hence there can be repetitions in the result of a query, but we can remove them: The result of a `SELECT` query, for instance, is a table, and SQL treats tables as multi-set, hence there can be repetitions in the result of a query, but we can remove them:
 
... ... SELECT Login, Major FROM STUDENT
1537 1614 ORDER BY Major, Name; ORDER BY Major, Name;
1538 1615 ~~~ ~~~
1539 1616
1617 `ORDER BY` order by ascending order by default.
1618
1540 1619 ### Aggregate functions ### Aggregate functions
1541 1620
1542 1621 You can use `MAX`, `SUM`, `MIN`, `AVG`, `COUNT`: You can use `MAX`, `SUM`, `MIN`, `AVG`, `COUNT`:
 
... ... SELECT Login AS Username FROM PROF;
1573 1652 +----------+ +----------+
1574 1653 ~~~ ~~~
1575 1654
1655 The purpose of aliases will be clearer as we study select-project-join queries.
1656
1576 1657 ## Three-Valued Logic ## Three-Valued Logic
1577 1658
1578 1659 Cf. [@Textbook6, 5.1.1], [@Textbook7, 7.1.1] Cf. [@Textbook6, 5.1.1], [@Textbook7, 7.1.1]
 
... ... You can test if a value is `NULL` with `IS NULL`.
1633 1714 INSERT INTO DEPARTMENT Values ('Hist', 'History', NULL); INSERT INTO DEPARTMENT Values ('Hist', 'History', NULL);
1634 1715 SELECT * FROM DEPARTMENT WHERE Head IS NULL; SELECT * FROM DEPARTMENT WHERE Head IS NULL;
1635 1716 SELECT * FROM DEPARTMENT WHERE Head IS NOT NULL; SELECT * FROM DEPARTMENT WHERE Head IS NOT NULL;
1636
1637 1717 SELECT COUNT(*) FROM GRADE WHERE Grade IS NULL; SELECT COUNT(*) FROM GRADE WHERE Grade IS NULL;
1638 1718 ~~~ ~~~
1639 1719
 
... ... We can further ask our DBMS to display the structure of the table we just create
2029 2109 DESCRIBE TableTest; -- Can be abbreviated as DESC TableTest; DESCRIBE TableTest; -- Can be abbreviated as DESC TableTest;
2030 2110 ~~~ ~~~
2031 2111
2032 And even ask to get back the code that would create the exact same structure:
2112 And even ask to get back the code that would create the exact same structure (but without the data!):
2033 2113
2034 2114 ~~~{.sqlmysql} ~~~{.sqlmysql}
2035 2115 SHOW CREATE TABLE TableTest; SHOW CREATE TABLE TableTest;
 
... ... You're all set! All you have to do is to quit, using the command
2078 2158 EXIT; EXIT;
2079 2159 ~~~ ~~~
2080 2160
2081
2082 2161 ## Exercises {-} ## Exercises {-}
2083 2162
2084 2163 Exercise +.# Exercise +.#
 
... ... Exercise +.#
2134 2213 : Write a statement that inserts the values `"Thomas"` and `4` into the table `TRAINS`. : Write a statement that inserts the values `"Thomas"` and `4` into the table `TRAINS`.
2135 2214
2136 2215 Exercise +.# Exercise +.#
2216 ~
2137 2217
2138 : If `PkgName` is the primary key in the table `MYTABLE`, what can you tell about the number of rows returned by the following statement? `SELECT * FROM MYTABLE WHERE PkgName = 'MySQL';`{.sqlmysql}.
2139
2140 Exercise +.#
2141
2142 : What is the difference between an implicit, an explicit, and a semantic constraint?
2143
2144 Exercise +.#explainfk
2145
2146 : What is a foreign key? Why is it useful?
2218 If `PkgName` is the primary key in the table `MYTABLE`, what can you tell about the number of rows returned by the following statement?
2219 `SELECT * FROM MYTABLE WHERE PkgName = 'MySQL';`{.sqlmysql}.
2147 2220
2148 2221 Exercise +.# Exercise +.#
2149 2222
 
... ... Exercise +.#
2151 2224
2152 2225 Exercise +.# Exercise +.#
2153 2226
2154 : If a database designer is using the `ON UPDATE SET NULL` for a foreign key, what mechanism is he implementing (i.e., describe how the database will react a certain operation)?
2227 : If a database designer is using the `ON UPDATE SET NULL` for a foreign key, what mechanism is (s)he implementing (i.e., describe how the database will react a certain operation)?
2155 2228
2156 2229 Exercise +.# Exercise +.#
2157 2230 ~ ~
 
... ... Exercise +.#
2161 2234 ~~~{.sqlmysql} ~~~{.sqlmysql}
2162 2235 FOREIGN KEY (DptNumber) REFERENCES DEPARTMENT(Number) FOREIGN KEY (DptNumber) REFERENCES DEPARTMENT(Number)
2163 2236 ON DELETE SET DEFAULT ON DELETE SET DEFAULT
2164 ON UPDATE CASCADE
2237 ON UPDATE CASCADE;
2165 2238 ~~~ ~~~
2166 2239
2167 2240 What happen to the rows whose foreign key `DptNumber` are set to `3` if the row in the `DEPARTEMENT` table with primary key `Number` set to `3` is… What happen to the rows whose foreign key `DptNumber` are set to `3` if the row in the `DEPARTEMENT` table with primary key `Number` set to `3` is…
 
... ... Exercise +.#
2175 2248 If the following is part of the design of a `WORKER` table: If the following is part of the design of a `WORKER` table:
2176 2249
2177 2250 ~~~{.sqlmysql} ~~~{.sqlmysql}
2178 FOREIGN KEY WORKER(DptNumber) REFERENCES DEPARTMENT(DptNumber)
2179 ON UPDATE CASCADE
2251 FOREIGN KEY WORKER(DptNumber) REFERENCES DEPARTMENT(DptNumber)
2252 ON UPDATE CASCADE;
2180 2253 ~~~ ~~~
2181 2254
2182 2255 What happen to the rows whose foreign key `DptNumber` are set to `3` if the row in the `DEPARTMENT` table with primary key `Number` set to `3` is… What happen to the rows whose foreign key `DptNumber` are set to `3` if the row in the `DEPARTMENT` table with primary key `Number` set to `3` is…
 
... ... Solution +.#
2360 2433 Solution +.# Solution +.#
2361 2434
2362 2435 : Yes. : Yes.
2363
2364 Solution +.#
2365 ~
2366 [@Textbook6, pp. 67--69] or [@Textbook7, pp. 157--158] reads:
2367 2436
2368 > Constraints on databases can generally be divided into three main categories:
2369 >
2370 >#. Constraints that are inherent in the data model. We call these **inherent model-based constraints** or **implicit constraints**.
2371 >#. Constraints that can be directly expressed in schemas of the data model, typically by specifying them in the DDL (data definition language, see Section 2.3.1). We call these **schema-based constraints** or **explicit constraints**.
2372 >#. Constraints that *cannot* be directly expressed in the schemas of the data model, and hence must be expressed and enforced by the application programs. We call these **application-based** or **semantic constraints** or **business rules**.
2373
2374 Solution +.#
2375
2376 : A forein key is an attribute (or column, field) referencing another attribute, which must be part of a primary key. It establishes connection between tables.
2377
2378 2437 Solution +.# Solution +.#
2379 2438
2380 2439 : We should use a referential triggered action clause, : `ON DELETE CASCADE`{.sqlmysql}. : We should use a referential triggered action clause, : `ON DELETE CASCADE`{.sqlmysql}.
 
... ... Solution +.#
2397 2456
2398 2457 Solution +.# Solution +.#
2399 2458 ~ ~
2400
2459 We could use the following:
2460
2401 2461 ~~~{.sqlmysql} ~~~{.sqlmysql}
2402 2462 SELECT Name, Address SELECT Name, Address
2403 2463 FROM TOURIST FROM TOURIST
 
... ... Solution +.#
2406 2466
2407 2467 Solution +.# Solution +.#
2408 2468
2409 : It selects all the attributes.
2469 : It selects all the attributes, it is a wildcard.
2410 2470
2411 2471 Solution +.# Solution +.#
2412 2472
 
... ... Solution +.#
2426 2486
2427 2487 Solution +.# Solution +.#
2428 2488
2429 : You can't have the `WHERE`{.sqlmysql} before `FROM`{.sqlmysql}.
2489 : You cannot have the `WHERE`{.sqlmysql} before `FROM`{.sqlmysql}.
2430 2490
2431 2491 Solution +.# Solution +.#
2432 2492
 
... ... Solution +.#
2447 2507
2448 2508 Solution +.# Solution +.#
2449 2509 ~ ~
2510 We could use the following:
2450 2511
2451 2512 ~~~{.sqlmysql} ~~~{.sqlmysql}
2452 2513 UPDATE PROF SET Name = 'Hugo Pernot' UPDATE PROF SET Name = 'Hugo Pernot'
 
... ... Solution +.#
2455 2516
2456 2517 Solution +.# Solution +.#
2457 2518
2458 : Yes, we could update more than one tuple at a time.
2519 : Yes, we can have select condition that does not use primary key. In that case, it could be the case that we update more than one tuple with such a command (which is not necessarily a bad thing).
2459 2520
2460 2521 Solution +.# Solution +.#
2461 2522
 
... ... Problem (TRAIN table and more advanced SQL coding) +.#train
2802 2863 @problem:train -- Question -.# @problem:train -- Question -.#
2803 2864 ~ ~
2804 2865 For each of the following questions, write a `SELECT` statement that would answer it: For each of the following questions, write a `SELECT` statement that would answer it:
2866
2805 2867 #. "What are the identification numbers of the trains?" #. "What are the identification numbers of the trains?"
2806 2868 #. "What are the names of the conductors with a "Senior" experience level?" #. "What are the names of the conductors with a "Senior" experience level?"
2807 2869 #. "What are the construction years of the "Surfliner" and "Regina" models that we have?" #. "What are the construction years of the "Surfliner" and "Regina" models that we have?"
 
... ... You can use **COFFEE**.1 to denote the first tuple (or row) in **COFFEE**, and s
2888 2950 @problem:coffee -- Question -.# @problem:coffee -- Question -.#
2889 2951 ~ ~
2890 2952
2891 Assuming that the referential triggered action clause `ON UPDATE CASCADE` is used for every foreign keys in this database, list the tuples modified by the following statements:
2953 Assuming that the referential triggered action clause `ON UPDATE CASCADE`{.sglmysql} is used for every foreign keys in this database, list the tuples modified by the following statements:
2892 2954
2893 2955 ~~~{.sqlmysql .numberLines} ~~~{.sqlmysql .numberLines}
2894 2956 UPDATE CUSTOMER SET FavCoffee = 001 UPDATE CUSTOMER SET FavCoffee = 001
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