Primary Key: A Primary Key in a database table is a field in the table that uniquely identifies every row or record present in the database table. 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.

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6. What is Race condition? How to prevent it? [2 marks] 7. How many synchronization methods do you know and compare the differences. [2 marks] 8. Explain what are the “mutual exclusion”, “deadlock”, “livelock”, and “eventual entry”, with the traffic intersection as an example like dinning philosophy. [2 marks] 9. For memory allocation, what are the difference between internal fragmentation and external fragmentation. Explain with an example. [2 marks] 10. How can the virtual memory map to the physical memory. Explain with an example. [2 marks]

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Chapter 3, Problem 2RQ

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Primary Key:

A Primary Key in a database table is a field in the table that uniquely identifies every row or record present in the database table.

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.

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