Primary Key:
A Primary Key in a
Example:
Students in Universities are assigned a unique registration number.
Therefore, in a STUDENT database table, the attribute “reg_no” acts as primary key.
Foreign Key:
Foreign Key is a column in a relational database table which provides a relation between two tables. It provides a cross reference between tables by pointing to primary key of another table.
Example:
In STUDENT database table, the attribute “reg_no” acts as primary key and in COURSE database table in which the student selects his or her course, the same “reg_no” acts as foreign key for the STUDENT table.
One-to-Many Relationship:
When one record in a database table is associated with more than one record in another table, the relationship between the two tables is referred as one to many relationship. It is also represented as1: M relationship. This is the opposite of many to one relationship.
One-to-One relationship:
When one record in a database table is associated with one and only one record in another table, the relationship between the two tables is referred as one to one relationship. It is also represented as1: 1 relationship.
Given database tables:
Table Name: EMPLOYEE
EMP_CODE | EMP_TITLE | EMP_LNAME | EMP_FNAME | EMP_INITIAL | EMP_DOB | STORE_CODE |
1 | Mr. | Williamson | John | W | 21-May-84 | 3 |
2 | Ms. | Ratula | Nancy | 09-Feb-89 | 2 | |
3 | Ms. | Greenboro | Lottie | R | 02-Oct-81 | 4 |
4 | Mrs. | Rumpersfro | Jennie | S | 01-Jun-71 | 5 |
5 | Mr. | Smith | Robert | L | 23-Nov-59 | 3 |
6 | Mr. | Renselear | Cary | A | 25-Dec-85 | 1 |
7 | Mr. | Ogallo | Roberto | S | 31-Jul-82 | 3 |
8 | Ms. | Johnson | Elizabeth | I | 10-Sep-88 | 1 |
9 | Mr. | Eindsmar | Jack | W | 19-Apr-55 | 2 |
10 | Mrs. | Jones | Rose | R | 06-Mar-66 | 4 |
11 | Mr. | Broderick | Tom | 21-Oct-72 | 3 | |
12 | Mr. | Washington | Alan | Y | 08-Sept-74 | 2 |
13 | Mr. | Smith | Peter | N | 25-Aug-64 | 3 |
14 | Ms. | Smith | Sherry | H | 25-May-66 | 4 |
15 | Mr. | Olenko | Howard | U | 24-May-64 | 5 |
16 | Mr. | Archialo | Barry | V | 03-Sep-60 | 5 |
17 | Ms. | Grimaldo | Jeanine | K | 12-Nov-70 | 4 |
18 | Mr. | Rosenburg | Andrew | D | 24-Jan-71 | 4 |
19 | Mr. | Rosten | Peter | F | 03-Oct-68 | 4 |
20 | Mr. | Mckee | Robert | S | 06-Mar-70 | 1 |
21 | Ms. | Baumann | Jennifer | A | 11-Dec-74 | 3 |
Table Name: STORE
STORE_CODE | STORE_NAME | STORE_YTD_SALES | REGION_CODE | EMP_CODE |
1 | Access Junction | 1003455.76 | 2 | 8 |
2 | Database Corner | 1421987.39 | 2 | 12 |
3 | Tuple Charge | 986783.22 | 1 | 7 |
4 | Attribute Alley | 944568.56 | 2 | 3 |
5 | Primary Key Point | 2930098.45 | 1 | 15 |
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Chapter 3 Solutions
Database Systems: Design, Implementation, & Management
- A Bank has many customers. Attribute for customer includes customer number, name, address (street, city, state and zip code), sex and date of birth. Customer can have multiple accounts. The bank does not allow join account (one account per customer). Type of account offer by the bank are Saving, Current and Fixed Deposit. Attribute for account are account no, account type, and account balance. Each of the account can only exist in a particular branch. Attribute for branch are branch no, branch name and address (street, city, state and zip code). Customer can open different account at different branch. Draw an ER diagram for the above situation. Identify the entity, attributes, primary key, relationship and multiplicity constraint in the ER diagram.arrow_forwardDefine second normal form. What types of problems might you encounter using tables that are not in second normal form?arrow_forwardList the changes you would need to make to your answer for Question 11 if the requirements change so that you must store the year and the semester in which a student took a course and received a grade.arrow_forward
- Considering the un-normalized relational table PROJECT below: PROJECT (Project Title, EmpeName, ManagerName, Location, Hours Work, ManagerPhone) The attributes of PROJECT table satisfy the following properties: Each project has many employees, Each employee may involve in one or more projects, Projects are managed by managers; there are many managers in the company, hence a project may be assigned to any one of the managers, but each manager manages only one project. Each project is located in a specific location, The number of hours an employee works at each project is determined by a project title and the name of an employee. Each manager has a telephone number. Normalize the relational table PROJECT into a minimal number of relational tables in BCNF. Use the functional dependencies to prove that each one of the relational tables obtained from the decomposition of the original table is in BCNF.arrow_forwardUse the XYZ Apartment Rental Company ERD shown on Figure 1 to answer questions 9 through 12: According to the XYZ Apartment Rental Company ER diagram, which of the following is NOTtrue? A building can have no builders A building can have one builder A building can have two builders A building can have more than two builders Answer: ____arrow_forwardSelect all the staff full names with the customer full names of the consignments they have worked on. Include staff that have not worked on any consignmentsarrow_forward
- Which type of relationship represents the rule that "Each vendor supplies multiple parts to our company and each part can be supplied by one or more vendors"? Question 43 options: 1) 1:M 2) 1:1 3) 0:1 4) M:Narrow_forwardSolve using SQL List the name of the division that has more projects than division of “human resource" Tables: Division (DID, dname, managerID) Employee (empID, name, salary, DID) Project (PID, pname, budget, DID) Workon (PID, EmpID, hours)arrow_forwardIndicate dependences and their type.arrow_forward
- Considering the un-normalized relational table PROJECT below: PROJECT (ProjectTitle, EmpeName, ManagerName, Location, HoursWork, ManagerPhone) The attributes of PROJECT table satisfy the following properties: Each project has many employees, Each employee may involve in one or more projects, Projects are managed by managers; there are many managers in the company, hence a project may be assigned to any one of the managers, but each manager manages only one project. Each project is located in a specific location, The number of hours an employee works at each project is determined by a project title and the name of an employee. Each manager has a telephone number. Normalize the relational table PROJECT into a minimal number of relational tables in BCNF. Use the functional dependencies to prove that each one of the relational tables obtained from the decomposition of the original table is in BCNF.arrow_forwardSelect the best answer from the given choices: Using the company schema, when creating the "works_on" table, the primary key should be specified as All of the answers are correct primary key (essn, pno) primary key (essn), primary key(pno) primary key (essn) and primary key(pno)arrow_forwardWhich type of relationship represents the rule that "Each vendor supplies multiple parts to our company and each part can be supplied by one or more vendors"? 1) 0:1 2) 1:M 3) M:N 4) 1:1arrow_forward
- A Guide to SQLComputer ScienceISBN:9781111527273Author:Philip J. PrattPublisher:Course Technology PtrNp Ms Office 365/Excel 2016 I NtermedComputer ScienceISBN:9781337508841Author:CareyPublisher:Cengage