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 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.
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
- For each table, identify the primary key and the foreign key(s). If a table does not have a foreign key, write None. FIGURE P3.17 THE CH03_TRANSCO DATABASE TABLESarrow_forwardCreate the table that results from applying an INTERSECT relational operator to the tables shown in Figure Q3.13. FIGURE Q3.13 THE CH03_VENDINGCO DATABASE TABLESarrow_forwardUsing the tables in Figure Q3.13, create the table that results from MACHINE DIFFERENCE BOOTH. FIGURE Q3.13 THE CH03_VENDINGCO DATABASE TABLESarrow_forward
- Use Figure Q3.13 to answer Questions 1317. FIGURE Q3.13 THE CH03_VENDINGCO DATABASE TABLES Write the relational algebra formula to apply a UNION relational operator to the tables shown in Figure Q3.13.arrow_forwardAn EMPLOYEES table was added to the JustLee Books database to track employee information. Display a list of each employee’s name, job title, and manager’s name. Use column aliases to clearly identify employee and manager name values. Include all employees in the list and sort by manager name.arrow_forwardHow is the processing of SQL DDL statements (such as CREATE TABLE) different from the processing required by DML statements?arrow_forward
- Problems 2224 are based on the following query: SELECT P_CODE, P_DESCRIPT, P_PRICE, P.V_CODE, V_STATE FROM PRODUCT P, VENDOR V WHERE P.V_CODE = V.V_CODE AND V_STATE = 'NY' AND V_AREACODE = '212' ORDER BY P_PRICE; Write the commands required to create the indexes you recommended in Problem 22.arrow_forwardExplain the concept of indexing in a relational database and its impact on query performance.arrow_forwardExplain the different types of tables in the ABAP dictionary.arrow_forward
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