23 Lecture - Physical Record and De-normalization

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23 Lecture

CS403

Midterm & Final Term Short Notes

Physical Record and De-normalization

Physical record refers to the actual data stored in a database on disk or other storage media. It includes the data fields, metadata, and any other information related to the data. De-normalization is the process of intentionally breaking normal


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  1. What is a physical record? a) The conceptual model of a database b) The actual data stored in a database on disk c) The logical model of a database d) The metadata associated with a database Answer: b) The actual data stored in a database on disk What is denormalization? a) The process of breaking normal form rules in a database to improve performance b) The process of improving the normalization of a database c) The process of removing redundant data from a database d) The process of optimizing database queries Answer: a) The process of breaking normal form rules in a database to improve performance What is the purpose of denormalization? a) To reduce the complexity of database queries b) To improve database performance c) To simplify the database design d) To increase data consistency in a database Answer: b) To improve database performance What are the risks of denormalization? a) Data redundancy and inconsistency b) Database performance degradation c) Increased query complexity d) All of the above Answer: d) All of the above What is data redundancy? a) The process of breaking normal form rules in a database to improve performance b) The duplication of data in a database c) The process of normalizing a database d) The metadata associated with a database Answer: b) The duplication of data in a database Which normal form does denormalization violate? a) First Normal Form b) Second Normal Form c) Third Normal Form d) Fourth Normal Form Answer: c) Third Normal Form What is the primary goal of normalization? a) To eliminate data redundancy b) To improve database performance c) To simplify the database design d) To increase data inconsistency in a database Answer: a) To eliminate data redundancy Which of the following is a disadvantage of denormalization? a) Reduced query complexity b) Increased data redundancy c) Improved database performance d) Simplified database design Answer: b) Increased data redundancy What is the consequence of data inconsistency? a) Increased query performance b) Improved data quality c) Increased risk of errors and inaccuracies d) Simplified database design Answer: c) Increased risk of errors and inaccuracies Which of the following is an example of denormalization? a) Combining two tables into one b) Normalizing a database c) Adding a new column to a table d) Creating a new index on a table Answer: a) Combining two tables into one


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  1. What is physical record in database design? Ans: Physical record refers to the way the data is stored on the storage devices like hard disks, CDs, or tapes. It specifies the number of bytes allocated to store each field or attribute of a table, the order in which the fields are stored, and the format of each field. What is denormalization in database design? Ans: Denormalization is a technique used in database design to improve query performance by adding redundant data to one or more tables. It is used in situations where there is a need for faster read performance than write performance. What are the advantages of denormalization? Ans: The advantages of denormalization include faster read performance, reduced complexity of queries, and improved query response time. It also eliminates the need for expensive joins and can improve the efficiency of data retrieval operations. What are the disadvantages of denormalization? Ans: The disadvantages of denormalization include increased storage space, increased complexity of data maintenance, and increased risk of data inconsistencies due to redundant data. What is a materialized view? Ans: A materialized view is a database object that contains the results of a query. It is a precomputed table that stores the results of a query so that the data can be retrieved more quickly. What is indexing in database design? Ans: Indexing is a technique used in database design to improve query performance. It involves creating a separate data structure that allows faster access to data based on certain criteria. What is clustering in database design? Ans: Clustering is a technique used in database design to improve query performance by physically grouping related data together on disk. What is partitioning in database design? Ans: Partitioning is a technique used in database design to improve query performance by dividing a large table into smaller, more manageable pieces called partitions. What is compression in database design? Ans: Compression is a technique used in database design to reduce the size of data stored on disk. It involves encoding data in a more compact format so that it takes up less space. What is backup and recovery in database design? Ans: Backup and recovery is a technique used in database design to protect data from loss or corruption. It involves making copies of the data and storing them in a secure location so that they can be restored in case of data loss or corruption.

Physical record refers to the way data is stored on a physical device such as a hard drive, solid-state drive, or tape drive. A database is designed to store data in a logical way, but it is the responsibility of the database management system to map the logical data model to a physical record format. De-normalization is the process of intentionally adding redundant data to a database to improve performance by minimizing the use of joins. It is typically done to speed up read operations, but can slow down write operations and increase the risk of data inconsistency. De-normalization is often used when it is difficult or impossible to optimize query performance through indexing or other techniques. De-normalization can be performed at different levels, including table, column, and index level. Common techniques for de-normalization include creating materialized views, using clustered indexes, and adding redundant columns. When considering de-normalization, it is important to balance the benefits of improved query performance against the potential risks of increased data redundancy and inconsistency. In general, de-normalization should be used sparingly and only when it is necessary to achieve acceptable performance levels. Overall, physical record and de-normalization are important considerations in the design and implementation of a database, and require careful analysis and planning to ensure that performance goals are met without sacrificing data integrity.

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