Learning MySQL Chapter 4 Homework

04ModelDesign/Homework.txt

@@ -0,0 +1,60 @@
+Q1. When would you use a weak entity?
+
+   One would use a weak entity to represent an entity that cannot be uniquely
+   identified by its attributes alone.
+
+   A weak entity requires additional attributes, typically in the form of one
+   (or more) foreign key(s) to uniquely identify it in the context of the
+   overall database.
+
+   In the folowing simple example, the childA and childB entities are weak
+   entities, each requiring a (foreign key) attribute from the strong parent
+   entity to generate the primary key for each child entity key.
+
+         +--------+
+      +--> parent <--+
+      |  +--------+  |
+      |              |
+   +--+-----+     +--+-----+
+   | childA |     | childB |
+   +--------+     +--------+
+
+
+Q2. Is it better to use entities instead of attributes?
+
+   Typically, it is better to use entities instead of attributes, but you
+   should ask yourself the following questions regarding the nature of the
+   object before making the final decision:
+
+   If the object is of direct interest to the database, it should be an entity.
+   And any information that describes it should be stored in attributes of
+   that entity.
+
+   If the object has components of its own, we must find a way of representing
+   those components; a separate entity might be the best solution.
+
+   If the object can have multiple instances, we must find a way to store
+   data on each instance. The cleanest way to do this is to represent the
+   object as a separate entity.
+
+   If the object is often nonexistent or unknown, it is effectively an
+   attribute of only some of the entities, and it would be better to model
+   it as a separate entity rather than as an attribute that is often empty.
+
+Q3. Alter and extend the music database ER model so that it can store
+    compilations, where a compilation is an album that contains tracks by two
+    or more different artists.
+
+A See Learning mysql 4-3.dia
+
+Q4. Create an ER diagram for an online media store using the following
+    requirements:
+
+   o There are two types of product: music CDs and video DVDs.
+   o Customers can buy any number of each product.
+   o For each CD, store the title, the artist’s name, the label (publisher),
+     and the price. Also store the number, title, and length (in seconds) of
+     each track on the CD.
+   o For each video DVD, store the title the studio name, and the price.
+
+A See Learning mysql 4-4.dia

05BasicSQL/homework.txt

@@ -22,28 +22,88 @@ in the WHERE. If you put the join clauses in the JOIN part, it's way more readab
 
 1) Use one or more SELECT statements to find out how many tracks are on New Order's Brotherhood album.
 
+   SELECT COUNT(track_id) FROM music.track INNER JOIN music.album USING (artist_id,album_id)
+          WHERE (SELECT artist_id FROM music.artist WHERE artist_name = "New Order")
+          AND album_name = "Brotherhood";
+
 2) Using a join, list the albums that we own by the band New Order
 
-3) With INSERT statements, add the artist Leftfield to the database. 
-For this new artist, add the album "Leftism" that has the following tracks:
-a. Release the Pressure (Time: 7.39)
-b. Afro-Melt (Time: 7.33)
-c. Melt (Time: 5.21)
-d. Song of Life (Time: 6.55)
-e. Original (Time: 6.00)
-f. Black Flute (Time: 3.46)
-g. Space Shanty (Time: 7.15)
-h. Inspection Check One (Time: 6.30)
-i. Storm 3000 (Time: 5.44)
-j. Open Up (Time: 6.52)
-k. 21st Century Poem (Time: 5.42)
-l. Bonus Track (Time: 1.22)
-
-The answer to this question should be the INSERT statement(s).
+   SELECT album_name FROM music.album INNER JOIN music.artist USING (artist_id)
+          WHERE artist_name = "New Order" ORDER BY album.album_name;
+
+3) With INSERT statements, add the artist Leftfield to the database.
+
+   For this new artist, add the album "Leftism" that has the following tracks:
+
+   a. Release the Pressure (Time: 7.39)
+   b. Afro-Melt (Time: 7.33)
+   c. Melt (Time: 5.21)
+   d. Song of Life (Time: 6.55)
+   e. Original (Time: 6.00)
+   f. Black Flute (Time: 3.46)
+   g. Space Shanty (Time: 7.15)
+   h. Inspection Check One (Time: 6.30)
+   i. Storm 3000 (Time: 5.44)
+   j. Open Up (Time: 6.52)
+   k. 21st Century Poem (Time: 5.42)
+   l. Bonus Track (Time: 1.22)
+
+   The answer to this question should be the INSERT statement(s).
+
+   SELECT 1+MAX(artist_id) FROM music.artist;
+   INSERT INTO music.artist VALUES(7, "Leftfield");
+
+   INSERT INTO music.track VALUES
+          (0, "Release the Pressure", 7, 0, 7.39),
+          (1, "Afro-Melt", 7, 0, 7.33),
+          (2, "Melt", 7, 0, 5.21),
+          (3, "Song of Life", 7, 0, 6.55),
+          (4, "Original", 7, 0, 6.00),
+          (5, "Black Flute", 7, 0, 3.46),
+          (6, "Space Shanty", 7, 0, 7.15),
+          (7, "Inspection Check One", 7, 0, 6.30),
+          (8, "Storm 3000", 7, 0, 5.44),
+          (9, "Open Up", 7, 0, 6.52),
+          (10, "21st Century Poem", 7, 0, 5.42),
+          (11, "Bonus Track", 7, 0, 1.22);
+
+   INSERT INTO music.played VALUES
+          (7, 0, 0, DEFAULT),
+          (7, 0, 1, DEFAULT),
+          (7, 0, 2, DEFAULT),
+          (7, 0, 3, DEFAULT),
+          (7, 0, 4, DEFAULT),
+          (7, 0, 5, DEFAULT),
+          (7, 0, 6, DEFAULT),
+          (7, 0, 7, DEFAULT),
+          (7, 0, 8, DEFAULT),
+          (7, 0, 9, DEFAULT),
+          (7, 0, 10, DEFAULT),
+          (7, 0, 11, DEFAULT);
 
 4) How long in minutes is the Leftism album you added in Question 3? Hint: use the
 SUM() aggregate function.
 
+    SELECT SUM(time) FROM music.track WHERE artist_id = 7 AND album_id = 0;
+    OR
+    SELECT SEC_TO_TIME(SUM(time) * 60) FROM music.track
+           WHERE artist_id = 7 AND album_id = 0;
+
 5) Change the time for the Original track on the Leftism album to 6.22.
 
+    UPDATE music.track SET time = 6.22
+           WHERE artist_id = 7
+           AND album_id = 0
+           AND track_name = "Original";
+
 6) Remove the 'Bonus Track' from the Leftism album,
+
+    DELETE FROM music.played
+           WHERE (album_id, track_id) IN
+           (select album_id,track_id FROM track
+           WHERE track_name = "Bonus Track");
+
+    DELETE FROM music.track
+           WHERE artist_id = 7
+           AND album_id = 0
+           AND track_name = "Bonus Track";

06DBStructures/homework.txt

@@ -1,32 +1,183 @@
-Chapter 6 Homework
+Chapter 6 Homework
 
 All exercises here concern the music database. 
 
-1. You’ve decided to store more information about artists and albums. Specifically,
-for artists, you want to store the names of people who have worked with the artist
-(for example, vocalists, guitarists, trumpeters, and drummers), when they began
-working with the artist, and when they stopped working with the artist (if they
-have done so).
+1 (a) You’ve decided to store more information about artists and albums.
+      Specifically, for artists, you want to store the names of people who
+      have worked with the artist (for example, vocalists, guitarists,
+      trumpeters, and drummers), when they began working with the artist,
+      and when they stopped working with the artist (if they have done so):
 
-For albums, you want to store the name of the album producer, when the album
-was released, and where the album was recorded. Design tables or columns that
-can store this information, and explain the advantages and disadvantages of your
-design. Choose the column types you need, explaining the advantages and disad-
-vantages of your choices.
+      create table sideman (
+        artist_id SMALLINT(5) NOT NULL DEFAULT 0,
+        sideman_id SMALLINT(5) NOT NULL DEFAULT 0,
+        sideman_name CHAR(128) DEFAULT NULL,
+        sideman_role CHAR(128) DEFAULT NULL,
+        started_working DATE NOT NULL DEFAULT 0,
+        stopped_working DATE NOT NULL DEFAULT 0,
+        PRIMARY KEY (artist_id,sideman_id)
+      );
 
-2. There are five types for storing temporal data: DATETIME, DATE, TIME, YEAR, and
-TIMESTAMP. Explain what each is used for, and give an example of a situation in
-which you would choose to use it. Note that http://palominodb.com/blog/2011/05/23/datetime-vs-timestamp
-has some useful information too.
+      For each one artist, there are N possible sidemen (male or female).
 
-3. You’ve decided to use the AUTO_INCREMENT feature. List the three requirements that
-must be met by the column you’re applying it to.
+      As a result, a sideman table should be created, which includes the
+      following information:
+
+      - name of the sideman
+      - their role (vocalist, guitarist, drummer, ...)
+      - when they started working with the artist
+      - when they stopped working with the artist
+
+      The above "create table" statement creates a table with those columns
+      and more:
+
+      - artist_id - small integer (SMALLINT) which identifies the artist that
+                    this sideman worked with. The column type is the same as
+                    the artist_id column in the artist table for table indexing
+                    purposes.
+      - sideman_id - small integer (SMALLINT) which uniquely identifies the
+                     sideman. Value of the column is 0-65535, suffient to
+                     identify an individual sideman
+      - sideman_name - first and last name of the side man. 128 bytes is large
+                       enough to identify them using "FirstName LastName" and
+                       small enough to allow mysql server to efficiently skip
+                       over table rows.
+      - sideman_role - what role the sideman performs. 128 bytes is large
+                       enough to specify their role and small enough to allow
+                       mysql server to efficiently skip over table rows.
+      - started_working - date the sideman started working with the artist in
+                          YYYY-MM-DD format. Summarizes desired information.
+      - stopped_working - date the sideman stopped working with the artist in
+                          YYYY-MM_DD format. Summarizes desired information.
+
+      The primary key for the table is a composite of the "artist_id" and
+      "sideman_id" columns.
+
+      The primary disadvantage of adding and populating the table is that
+      it will increase the size of the database.
+
+      It's primary advantage is that it succinctly specifies the desired
+      sideman information in minimal database size and used disk space.
+
+  (b) For albums, you want to store the name of the album producer, when the
+      album was released, and where the album was recorded. Design tables or
+      columns that can store this information, and explain the advantages and
+      disadvantages of your design. Choose the column types you need,
+      explaining the advantages and disadvantages of your choices.
+
+      In order to store the name of the album producer, when the album was
+      released and where it was recorded, it is best to add that information
+      to the existing album table.
+
+      This can be done by appending the following columns to the table:
+
+      - producer_name CHAR(128) DEFAULT NULL
+      - release_date DATE DEFAULT 0
+      - recorded_site CHAR(128) DEFAULT NULL
+
+      or dropping and recreating the table with those columns:
+
+      create table album (
+        artist_id SMALLINT(5) NOT NULL DEFAULT 0,
+        album_id SMALLINT(4) NOT NULL DEFAULT 0,
+        album_name CHAR(128) DEFAULT NULL,
+        producer_name CHAR(128) DEFAULT NULL,
+        release_date DATE DEFAULT 0,
+        recorded_site CHAR(128) DEFAULT NULL,
+        PRIMARY KEY  (artist_id,album_id)
+      );
+
+      The 128 byte producer_name column is large enough to contain the
+      "FirstName LastName" of the producer.
+
+      The release date summarizes the albums release date in YYYY-MM-DD format,
+      which is what we want.
+
+      The 128 byte recorded site (where the album was recorded) column is large
+      enough to contain the name of the studio or town/city where the album was
+      recorded.
+
+      The primary disadvantage of adding these columns to the album table is
+      that it will increase the size of the database.
+
+      But the inclusion of these columns commits data that may be valuable to
+      the end user.
+
+2. There are five types for storing temporal data: DATETIME, DATE, TIME, YEAR,
+   and TIMESTAMP. Explain what each is used for, and give an example of a
+   situation in which you would choose to use it. Note that
+   http://palominodb.com/blog/2011/05/23/datetime-vs-timestamp has some useful
+   information too.
+
+   DATETIME - Stores and displays a date and time in the format "YYYY-MM-DD
+              HH:MM:SS" for the range 1000-01-01 00:00:00 to 9999-12-31
+              23:59:59. It can be input to a mysql table in multiple forms,
+              but is stored internally as YYYY-MM-DD HH:MM:SS.
+
+              Such a column in a mysql table row would be useful for tracking
+              the delivery of parcel or package.
+
+   DATE - Stores and displays a date in the format YYYY-MM-DD for the range
+          1000-01-01 to 9999-12-31. Dates must always be input as year, month,
+          and day triples, but the format of the input can vary.
+
+          Such a column in a mysql table row would be useful for tracking the
+          date when a person was born and when they died.
+
+   TIME - Stores a time in the format HHH:MM:SS for the range -838:59:59 to
+          838:59:59. Times must always be input in the order days, hours,
+          minutes, and seconds, using the following formats:
+
+          DD HH:MM:SS, HH:MM:SS, DD HH:MM, HH:MM, DD HH, or SS
+
+          Such a column in a mysql table row would be useful for tracking the
+          time to complete a run.
+
+   YEAR - Stores the year in two-digit or four-digit format.
+
+          Such a column in a mysql table row would be useful for tracking the
+          year a car was manufactured.
+
+   TIMESTAMP - Stores and displays a date and time pair in the format
+               "YYYY-MM-DD HH:MM:SS" for the range 1970-01-01 00:00:00 to
+               sometime in 2037.
+
+               This column type is similar to DATETIME, but provides an auto-
+               update to the current date functionality, which is useful.
+
+               Because of this auto-update functionality, this column type is
+               useful in any situation when you wish to record the time when
+               another element in the table row is added or updated.
+
+               For example, when the status of a flight has changed.
+
+3. You’ve decided to use the AUTO_INCREMENT feature. List the three
+   requirements that must be met by the column you’re applying it to.
+
+   The AUTO_INCREMENT feature has the following requirements:
+
+   o The column it is used on must be indexed.
+   o The column that is it used on cannot have a DEFAULT value.
+   o There can be only one AUTO_INCREMENT column per table.
 
 4. Why can only one column in a table have the AUTO_INCREMENT feature?
 
+   MySQL’s proprietary AUTO_INCREMENT feature allows you to create a unique
+   identifier for a table row.
+
+   Consequently, if a table had two (or more) table indexes with the
+   AUTO_INCREMENT feature, it may no longer have a unique value to identify
+   each row.
+
 5. Using the monitor, create a table with the following statement:
-mysql> CREATE TABLE exercise (field1 INT(3));
-Using the ALTER TABLE statement, make field1 the primary key, carrying out any
-additional steps you need to make this possible. Add a second column, field2, of
-type CHAR(64) with a DEFAULT 5 clause. Create an index on a prefix of 10 characters
-from field2.
+
+   mysql> CREATE TABLE exercise (field1 INT(3));
+
+   Using the ALTER TABLE statement, make field1 the primary key, carrying out any
+   additional steps you need to make this possible. Add a second column, field2, of
+   type CHAR(64) with a DEFAULT 5 clause. Create an index on a prefix of 10 characters
+   from field2.
+
+   ALTER TABLE exercise ADD PRIMARY KEY (field1);
+   ALTER TABLE exercise ADD field2 CHAR(64) DEFAULT 5;
+   ALTER TABLE exercise ADD INDEX (field2(10));