Database Design - Section 11. Instructor Guide

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Victoria Hunter
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3 Table of Contents...1 Lesson 1 - What About Me?...1 What Will I Learn?...2 Why Learn It? Try It / Solve It...5 Lesson 2 - Drawing Conventions for Readability...6 What Will I Learn?...7 Why Learn It? Try It / Solve It...17 Lesson 3 - Generic Modeling...22 What Will I Learn?...23 Why Learn It? Try It / Solve It...33 Lesson 4 - Introduction to Relational Database Concepts...35 What Will I Learn?...36 Why Learn It? Try It / Solve It...49 Lesson 5 - Review...50 What Will I Learn?...51 Why Learn It? Try It / Solve It...54 Page i

5 Lesson 1 - What About Me? Lesson 1 - What About Me? Lesson Preparation This career skills lesson will help students analyze and understand IT career options and education requirements based on interests, abilities, aptitudes, and accomplishments. The Internet or a school career center or person has numerous career inventory sites. Students do several inventories and identify their strengths, interests, and aptitudes. They will then write an essay - - "What I Know About Me" -- that will be used in the identification of careers. This ties to the previous lesson on IT leaders. If you want to cover the connections in class, make sure you allow for time to do so after they write their essays. What to Watch For None. Connections Go back to Leaders in Information Technology (previous lesson). Which of the IT leaders you researched can you most identify with? What skills, interests, or personal traits do you have that you feel you share with this person? Give an example. Who would you most want to emulate? How would you go about doing this? Page 1

6 What Will I Learn? What Will I Learn? Page 2

7 Why Learn It? Why Learn It? Page 3

8 These are a number of different sites for interest and skills inventory research. Review these sites and choose which will work best with your students. Write them on the board for class. U.S. government site Visit ICPAC at for FAQs and activities on how to choose a career based on your interests provides a list of basic skills that high-school students need to get a job The school's career center/person can also provide career inventories. Page 4

9 Try It / Solve It Try It / Solve It Try It / Solve It It may help to give students an outline to base their essay on, such as: 1. My interests: What do I love to do? What do I spend most of my spare time doing? What would I do for free because I enjoy it so much? 2. My skills: What can I do? What am I good at (sports, writing, organizing club activities, math, etc.)? What are my best subjects? What am I always getting compliments on? 3. Possible careers: Where do I go from here? Based on my interests, skills, and research, what careers would be most suited to me? What careers would I like to try and why? Encourage students to broaden their scope by considering at least three different types of jobs/careers. It is too early for them to get locked into narrow choices. The essay should be at least two pages long. They should list the websites they used to find out information about careers. For each possible career, they should list job titles, sample job descriptions, starting salary, average salary, and types of companies that would be employers. Students can start writing the essay in class but can finish it afterward. The assignment should be turned in within two days (by Section 11, Lesson 2). Please use the grading guidelines established at your school to evaluate comparable student work. Page 5

10 Lesson 2 - Drawing Conventions for Readability Lesson 2 - Drawing Conventions for Readability Lesson Preparation Although drawing conventions were covered in Section 3, Lesson 2, at this point students will have seen and drawn more complicated ERDs. The issues of drawing for clarity and readability and dividing a big ERD up into functional areas need to be addressed here. What to Watch For None. Connections Brainstorm a list of conventions that are understood by most people that seem to be "learned" along the way. For example, the fork goes on the left, people shake hands when meeting others, there are three numbers on each row on a telephone, the cold water faucet is on the right, etc. How do these conventions make things easier for us? Answer: They tell us what to expect and help us behave appropriately. Page 6

11 What Will I Learn? What Will I Learn? Page 7

12 Why Learn It? Why Learn It? Why Learn It? Ask the class what they think is wrong with this ERD. (It looks quite messy.) Point out that it accurately models the DJ business, but is it readable? (No, it could be a lot better.) How would they improve on it? Possible answers: - Avoid criss-crossing lines. - Increase white space so that the relationships don t overlap. - Use consistent font types, sizes, and styles. Page 8

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14 This is a review of a convention discussed previously. We say the crows are flying south because the crow s feet are pointing north, as in JOB ASSIGNMENT and EVENT. We say the crows are flying east toward PARTNER and CLIENT, because the crow s feet are pointing west. Discuss why there would be more instances of JOB ASSIGNMENT than PARTNER or EVENT. This is because each event may have many partners working on it, and each one would be a job assignment. Similarly, there would be more instances of EVENT than CLIENT or SPACE (PUBLIC or PRIVATE). Page 10

15 Why is JOB ASSIGNMENT an important entity? It is important because it stores data on which partner is working on an event, what the status is, etc. This is information that is important in running the day-to-day business for DJs on Demand. Similarly, EVENT is an important entity -- it is the main thing on which the DJ business is built. Page 11

16 Ask the class to find the crows that are flying north (to CLIENT), south (to PUBLIC and PRIVATE SPACE), east (to PARTNER), and west (to EVENT). Point out that this is still a readable diagram. Which are the high-volume entities in the model? Answer: EVENT and JOB ASSIGNMENT. They have the most number of relationships to other entities. Page 12

17 These diagrams convey the same information, but the one on the right is more readable. Do not sacrifice readability for space. Page 13

18 Although it is important to have a big diagram that shows the whole picture (even if it has to be printed on a plotter or taped together from smaller pieces of paper), it can be useful to have smaller ERDs for the different functional areas. Page 14

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21 Try It / Solve It Try It / Solve It Try It / Solve It Assessment: Review your Global Fast Foods data model so far and redraw it for readability. 1. Create a diagram that contains all the entities, attributes, and relationships you ve identified. Include unique identifiers. Answer: The Global Foods ERD can be drawn in several ways that are clear and readable. Look for adherence to basic conventions such as no crossing relationship lines, relationship names on either side of the relationship line, no overlapping relationship names, enough white space, etc. 2. Create a smaller diagram that contains all the entities that would be of interest to the order taker. Answer: The diagram should include entities that would be of concern to the order taker: FREQUENT DINER CARD, ORDER, ORDER LINE, FOOD ITEM, REGULAR MENU, PROMOTIONAL MENU. Page 17

22 Try It / Solve It Try It / Solve It Try It / Solve It This activity is to be done only if there is extra time. It can also be assigned as homework. One possible solution to this activity is presented in: One possible solution for Summit Sporting Goods Activity Some students may not be familiar with the term wholesale. Explain that a wholesale company buys large quantities of items from manufacturers at a substantial discount. We don t normally shop at a wholesale store. Their customers are the retail stores (where we do shop). Retail stores buy items from wholesale stores. They will normally pay a little more than the wholesaler because they are buying smaller quantities. Page 18

23 Try It / Solve It Try It / Solve It Page 19

24 Try It / Solve It Try It / Solve It Try It / Solve It You may have to explain the terms reorder point and good credit standing. Reorder point: When items are kept in stock (or inventory), the number of items decreases over time, as they are sent out to customers who order them. When the number of items goes down to a certain amount, the company decides to purchase more to make sure they don t run out. This certain amount is the reorder point. Explain that the reorder point is decided on by the company depending on several factors -- frequency of orders, cash flow, time of year, etc. Good credit standing: Refers to a rating or comment assigned to a customer s credit account. If the customer pays on time, then the account is said to be in good credit standing. If the customer misses payments or pays late, then the credit standing may be less than good. Page 20

25 Try It / Solve It Try It / Solve It Try It / Solve It You may have to explain the term commission. It is an amount paid to salespersons for every item they sell or transaction they make. This is usually a percentage of the transaction amount. Depending on the business, some salespersons get a regular salary, plus a commission. Others work on commission only. Page 21

26 Lesson 3 - Generic Modeling Lesson 3 - Generic Modeling Lesson Preparation Understanding generic models can be a challenge, because it requires the learner to go up one or two levels of abstraction. To illustrate the concepts in this lesson, we will make use of several data examples as well as the ERDs. What to Watch For None. Connections None. Page 22

27 What Will I Learn? What Will I Learn? Page 23

28 Why Learn It? Why Learn It? Why Learn It? Make sure that students understand the meaning of the word generic. You may want to use other examples, such as brand-name jeans as opposed to jeans with no label. There may be some negative associations with the word generic -- as in cheap, not as good, etc. Explain that in the data-modeling world, generic models are neither cheap nor a poor substitute. In fact, they can be more complex, but more flexible, as the lesson will illustrate. Page 24

29 The graphic shows the generic model with a single entity ARTICLE. This can also be modeled with subtypes of SHIRT, SKIRT, DRESS, PANTS, etc. It would still reduce the number of entities. Point out that with the generic model, the common attributes can keep their mandatory nature (length, material), but other attributes specific to one type of ARTICLE must become optional. For example: neck size and sleeve length are mandatory for a SHIRT, but they need to be optional in the generic model because other articles (SKIRT, DRESS, PANTS) don t have that attribute. Ask students: What would happen to the generic model if we had to add 10 new ARTICLE types, each with their own attributes? Answer: New attributes would have to be added to the entity ARTICLE. If the new types did not include the same mandatory attributes (length, material), those attributes would now have to be changed to optional. The problem is compounded if subtypes were modeled, because each new type would mean the creation of a new subtype. These are significant changes to the model. Page 25

Walk students through the data to help them understand the model. DNM105 is the ID for a shirt with length of 40, made of denim material, with a neck size of 16, and a sleeve length of 33.

30 Walk students through the data to help them understand the model. DNM105 is the ID for a shirt with length of 40, made of denim material, with a neck size of 16, and a sleeve length of 33. LIN200 is the ID for a skirt with a length of 22, made of linen material, with a waistband type of elastic, and a hem circumference of 60. To understand the data in ARTICLE, you have to look at the data in ARTICLE TYPE. We have not discussed entity-to-table mapping yet, so some students may be confused as to why ARTICLE TYPE name is listed as a column under ARTICLE. Remind them that this is sample data, and that the relationship from ARTICLE to ARTICLE TYPE suggests that the ARTICLE TYPE name will be part of the data that is stored in ARTICLE. Data is part of the physical implementation of the conceptual model, which we will learn about later. This is a more flexible model than the first one because the addition of types of articles simply involves adding instances to ARTICLE TYPE and ARTICLE. The problem occurs if the new types have more attributes than the maximum number defined in the model. This will mean modifying both ARTICLE TYPE and ARTICLE entities to add attributes. Therefore, this model is good if the number of attributes is known and fairly fixed. Page 26

31 You may also want to point out that this model can make the data look more complex. The value of each attribute can be different depending on the type of ARTICLE instance. For example, Property 4 can be a number for one type of article and a character string for another type of article. This means that the data type of each attribute in ARTICLE has to be fairly generic as well to hold all kinds of data. Page 27

32 Walk students through the data to help them understand the model. DNM105 is the ID for a shirt with length of 40, made of denim material, with a neck size of 16, and a sleeve length of 33. LIN200 is the ID for a skirt with a length of 22, made of linen material, with a waistband type of elastic, and a hem circumference of 60. To understand the data in ARTICLE, you have to look at the data in ARTICLE TYPE. We have not discussed entity-to-table mapping yet, so some students may be confused as to why ARTICLE TYPE name is listed as a column under ARTICLE. Remind them that this is sample data, and that the relationship from ARTICLE to ARTICLE TYPE suggests that the ARTICLE TYPE name will be part of the data that is stored in ARTICLE. Data is part of the physical implementation of the conceptual model, which we will learn about later. This is a more flexible model than the first one because the addition of types of articles simply involves adding instances to ARTICLE TYPE and ARTICLE. The problem occurs if the new types have more attributes than the maximum number defined in the model. This will mean modifying both ARTICLE TYPE and ARTICLE entities to add attributes. Therefore, this model is good if the number of attributes is known and fairly fixed. Page 28

33 You may also want to point out that this model can make the data look more complex. The value of each attribute can be different depending on the type of ARTICLE instance. For example, Property 4 can be a number for one type of article and a character string for another type of article. This means that the data type of each attribute in ARTICLE has to be fairly generic as well to hold all kinds of data. Page 29

Instructions: Again, you will need to walk the students through the data to help clarify the model. ARTICLE TYPE stores the different kinds of articles (shirt, skirt, pants, etc.).

34 Instructions: Again, you will need to walk the students through the data to help clarify the model. ARTICLE TYPE stores the different kinds of articles (shirt, skirt, pants, etc.). ARTICLE stores the IDs of each article (DNM105 is the ID for a shirt, LIN200 is the ID for a skirt, etc.). PROPERTY stores the descriptors for each article type (SHIRT has a length, material, neck size, etc. SKIRT has a length, etc.). ARTICLE PROPERTY VALUE stores the actual value for each property of each article (DNM105, which is a shirt, has a length of 40, material of denim, neck size of 16; LIN200, which is a skirt, has a length of 22). We have not discussed entity-to-table mapping yet, so some students may be confused as to why ARTICLE TYPE Name is listed as a column under PROPERTY. Remind them that this is sample data, and that the relationship from ARTICLE to PROPERTY suggests that the ARTICLE TYPE name will be part of the data that is stored in PROPERTY. Data is part of the physical implementation of the conceptual model, which we will learn about later. Point out that this is the most flexible model so far. We can add any number of article types with different types and any number of attributes. Again, while the structure gives us a lot of flexibility, it makes the data more complex. To understand the ARTICLE PROPERTY Page 30

35 VALUE, you must know the ARTICLE identifier, the PROPERTY number, and the ARTICLE type. Instructions: Page 31

36 The benefits of generic models are most apparent when the business requirements change often. There will be a need to add new entities and attributes in the future, which cannot be specified at this time. A generic solution is more flexible and will accommodate change without too much impact to the model. However, it does make looking at the data more complex. This means that end users who want to access the database will have to write more complex SQL queries, and developers who write applications for the database will need to add more complexity to their code as well. Page 32

Try It / Solve It Try It / Solve It Try It / Solve It Instructions: Although there are relationships between STAFF and other entities in the model, tell

37 Try It / Solve It Try It / Solve It Try It / Solve It Instructions: Although there are relationships between STAFF and other entities in the model, tell students not to worry about it right now. We will encounter and discuss similar issues when we look at supertype implementation in a later lesson. Page 33

38 Instructions: Although there are relationships between STAFF and other entities in the model, tell students not to worry about it right now. We will encounter and discuss similar issues when we look at supertype implementation in a later lesson. Page 34

39 Lesson 4 - Introduction to Relational Database Concepts Lesson 4 - Introduction to Relational Database Concepts Lesson Preparation This lesson talks about relational databases, primary keys, foreign keys, and data integrity. This will help with the transition to SQL in the upcoming sections. Encourage the students to realize that they are learning a new set of terminology. An entity is not a table, and an attribute is not a column. We will be transforming (exchanging) one set of objects (ER constructs) into another (data design constructs). What to Watch For None. Connections Remind students that they have seen user-defined integrity before. These are the business rules that cannot be represented in the conceptual model and must be documented. This is the reason for the documentation -- to make sure that the programmers write extra code to enforce these rules in the database! Relate to other processes where the model becomes reality, such as an architect drawing becomes a house, planning for a party and the actual party, or a prototype becomes a product. Page 35

40 What Will I Learn? What Will I Learn? Page 36

41 Why Learn It? Why Learn It? Page 37

42 Explain that each row of data describes an employee. Each column is an attribute of that employee. If we wanted to find out the last name and department number of employee number 210, we would need to access the third row in the table, and then find the values for fname and dept_no for that row. But how do we find the correct row in the first place? Would we have to go through the whole table and look at every row? Answer: No. (Move on to next page.) Page 38

43 Ask students if they understand the SQL code just by reading it. They should have some ideas because of its English-like syntax. Page 39

44 Explain that * after SELECT means we want all the columns in the table. SQL allows us to access the whole table or just parts of the table, depending on what comes after SELECT and what is specified in the WHERE clause. Page 40

45 Point out that in ACCOUNTS, bank_no is not unique and acct_no is not unique. However, the combination of bank_no and acct_no is unique. Page 41

46 Ask students to point out the rows in each table that violate the rule that no part of the primary key can be null. Answer: Second row in EMPLOYEES, second row in ACCOUNTS. These rows violate entity integrity. Page 42

47 Ask students what makes emp_no and payroll_id good candidates for the primary key? Answer: They are both unique and not null. Page 43

48 Ask students why having alternate or unique keys can be useful? Answer: It s another way to locate a record. If you forget your employee ID, but know your payroll ID (or have a payroll stub with the ID on it), then you can still access your employee record. Page 44

49 Point out that if the foreign key (dept_no) in EMPLOYEES has a value of 10, then there needs to be a row in DEPARTMENTS with a dept_no of 10. Otherwise, it is a violation of referential integrity. You can also explain this in business terms, by saying that an employee can t belong to a department that doesn t exist. Page 45

50 Point out that in the example, shelf_no is part of the primary key of BOOKS. It is also a foreign key to SHELVES. Since it is part of the PK of BOOKS, it cannot be null. Page 46

Explain to students that the data type for the columns bank_no, acct_no, and balance is numeric. The number in parentheses indicates how big the numeric value can be.

51 Explain to students that the data type for the columns bank_no, acct_no, and balance is numeric. The number in parentheses indicates how big the numeric value can be. A data type of date means the value must be a valid date. Not null in the Optionality column means that the column is mandatory. Which rows in the table violate column integrity? Answer: Second and fourth rows Page 47

52 This is a summary of the data-integrity rules we ve covered. Page 48

53 Try It / Solve It Try It / Solve It Try It / Solve It Assessment: CLIENTS table Entity integrity: ID for Sarika Patel should not be null. EVENTS TABLE Column integrity: Cost for Collins wedding (event id = 17) is not numeric. Column integrity: Date for Collins rehearsal dinner (event id = 25) is not a valid date format. Referential integrity: There is no client 77 in the CLIENTS table (event id = 50). Referential integrity: There is no theme corresponding to BB in the THEMES table (event id = 15). Page 49

54 Lesson 5 - Review Lesson 5 - Review Lesson Preparation Review lesson content for fifteen minutes before you administer the quiz. This is a good time to answer questions, clarify recently learned concepts and terminology, and go over some of the practice solutions from previous lessons. What to Watch For None. Connections None. Page 50

55 What Will I Learn? What Will I Learn? Page 51

56 Why Learn It? Why Learn It? Page 52

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58 Try It / Solve It Try It / Solve It Try It / Solve It Allow 20 minutes for the quiz and 10 minutes for assessment/discussion afterward. Assessment: You may want to encourage students to retake the quiz until they achieve a passing score. Or you may prefer to allow only one attempt at the quiz. Have students work in small groups to review what they missed on the quiz. Based on what types of questions they missed, have students write out the rules (e.g., rules for subtypes). Have a member from each group present a summary back to the class about what areas their group can improve. Page 54

Database Design. 8-4 Drawing Conventions for Readability. Copyright 2015, Oracle and/or its affiliates. All rights reserved.

Database Design. 8-4 Drawing Conventions for Readability. Copyright 2015, Oracle and/or its affiliates. All rights reserved. 1 Database Design 8-4 Objectives This lesson covers the following objectives: Apply the Oracle drawing conventions to a data model diagram Identify high volume entities in a data model diagram and explain