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 more than one record in a database table is associated with only one record 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 relationships:
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 relationships. It is also represented as1: M relationship. This is the opposite of many to one relationship.
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.
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Chapter 3 Solutions
Database Systems: Design, Implementation, & Management
- Create 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_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_forwardplease 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_forward
- List the name of employee who is working on a project with the budget that is below this project's divisional average project budget (use correlated subquery).arrow_forwardSelect all managers whose firstname starts with letter M and department they lead have less than 10 employees. Present manager and employee count in the result set. Order result set by employee count in descending order.arrow_forwardNormalize the following form into UNF 1NF, 2NF and 3NF. Show primary keys and foreign keys for all the normalized tables (from 3NF). Employee Task Record Form EmployeelD : 587 Employee Name: Smith Department ID: D1 DeparmentName : IT Task ID Task Name Duration Supervisor ID | Supervisor Name Emp_TaskJoin_Date Designing Drawing Reporting T1 70hrs S1 Khalfan 12/12/2019 T2 56hrs S2 Fatma 01/10/2020 T3 60hrs S3 Haitham 11/11/2020arrow_forward
- Please design a Task durations and a Dependencies table, and also calculate the Task durations and the Dependencies using the image below:arrow_forwardPlease answer my questionsarrow_forwardGarden Glory is a partnership that provides gardening and yard maintenance services to individuals and organizations. Garden Glory is owned by two partners. They employ two office administrators and a number of full- and part-time gardeners. Garden Glory will provide one-time garden services, but it specializes in ongoing service and maintenance. Many of its customers have multiple buildings, apartments, and rental houses that require gardening and lawn maintenance services. Create a sample list of owners and properties. Your list will be similar in structure to that in Figure 1-34 g, but it will concern owners and properties rather than owners and pets. Your list should include, at a minimum, owner name, phone, and billing address, as well as property name, type, and address. B. Describe modification problems that are likely to occur if Garden Glory attempts to maintain the list in a spreadsheet. C. Split the list into tables such that each has only one theme. Create appropriate…arrow_forward
- Create a new table named ScheduledClients to contain client’s name, the scheduled date of service, task ID, description of the service, and the quoted price.arrow_forward1- Select all those professors who age in the range 30 to 40 and don't have any rank. 2- List all professors whose name begins with 'A' or end with ‘L’ and age large than 30 3- Count the number of different professors names 4- add new column to project table with constraint unique and Delete the record for the professors whose name is ‘Alex’arrow_forwardHow is the order of characteristics in a result table altered?arrow_forward
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