Concept explainers
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.
Many-to-One relationship:
When one record in a database table is associated with one or more records in another table, the relationship between the two tables is referred as many-to-one relationship. It is also represented as M: 1 relationship.
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.
ENTITY- RELATIONSHIP DIAGRAM (ERD):
Entity- Relationship Diagram is also known as ER Diagram. It is used to define the conceptual view of the database as viewed by the end user. It is used to depict the database’s main components: entities, relationships and attributes.
CROW FOOT ERD:
The Crow Foot ERD is an Entity Relationship Diagram which is used to represent the cardinalities present in the basic ER diagram. It is used to represent the relationships present between two tuples or tables present in the database.
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 |
Trending nowThis is a popular solution!
Chapter 3 Solutions
Database Systems: Design, Implementation, & Management
- please use the picture to answer the following question Normalize below user view to the third normal form. Show all steps (UNF, 1NF, Dependencies, 2NF, 3NF).arrow_forwardBased on the ERD below, display all columns in the JOB table for those job descriptions that have both analysts and engineers within the description name. (Hint: You will use a “Like” phrase.)arrow_forwardCreate correlated and noncorrelated subqueries and understand when to use.arrow_forward
- Display the CID, CName, RID and RType from both tables using the NATURAL JOIN clause.arrow_forwardDisplay the country names and region names where no warehouse is located in them. Use set operators to create this report and provide the exact sorting as below.arrow_forwardTo be more specific, what are the criteria for the page table?arrow_forward
- how is the ProductID field in the Product table specified to be required? Why is it a required attribute?arrow_forwardAlter the DETAILRENTAL table to include a derived attribute named DETAIL_DAYS-LATE to store integers of up to three digits. The attribute should accept null values.arrow_forwardCreate a table named REP_CONTRACTS containing the columns listed in the following chart A composite PRIMARY KEY constraint including the Rep_ID, Store_ID, and Quarter columns should be assigned. In addition, FOREIGN KEY constraints should be assigned to both the Rep_ID and Store_ID columns.arrow_forward
- You’re creating a new table consisting of three columns: Col1, Col2, and Col3. Col1 should be the primary key and can’t have any NULL values, and each entry should be unique. Col3 must not contain any NULL values either. How many total constraints do you have to create? 1 2 3 4arrow_forwardEnsure that the only legal values for the BDRMS column in the CONDO_UNIT table are 1, 2, or 3.arrow_forwardThe FOREIGN KEY constraint should be added to which table? the table representing the “one” side of a one-to-many relationship the parent table in a parent-child relationship the child table in a parent-child relationship the table that doesn’t have a primary keyarrow_forward
- Database Systems: Design, Implementation, & Manag...Computer ScienceISBN:9781305627482Author:Carlos Coronel, Steven MorrisPublisher:Cengage LearningNp Ms Office 365/Excel 2016 I NtermedComputer ScienceISBN:9781337508841Author:CareyPublisher:CengageA Guide to SQLComputer ScienceISBN:9781111527273Author:Philip J. PrattPublisher:Course Technology Ptr
- Database Systems: Design, Implementation, & Manag...Computer ScienceISBN:9781285196145Author:Steven, Steven Morris, Carlos Coronel, Carlos, Coronel, Carlos; Morris, Carlos Coronel and Steven Morris, Carlos Coronel; Steven Morris, Steven Morris; Carlos CoronelPublisher:Cengage Learning