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.
Entity Integrity:
Entity Integrity is a
- The primary key of one database table row must not match the primary key of any other row present in the table.
- No component of primary key must be null.
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Chapter 3 Solutions
DATABASE SYSTEMS (LL)-W/ACCESS>CUSTOM<
- Do the tables exhibit referential integrity? Answer yes or no, and then explain your answer. Write NA (Not Applicable) if the table does not have a foreign key. FIGURE P3.17 THE CH03_TRANSCO DATABASE TABLESarrow_forwardDo the tables exhibit referential integrity? Answer yes or no, and then explain your answer. Write NA (Not Applicable) if the table does not have a foreign key.arrow_forwardFor 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_forward
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