Database Fundamentals and Queries
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Questions and Answers

Besides implementing security measures, what is one other key role of a database administrator at Bucharesti School?

Approving data access.

Outline one method a Database Management System (DBMS) can employ to ensure the confidentiality and integrity of students' personal data.

Access controls: Effective and efficient access control so that end users can access only the data or programs for which they have privileges.

Explain how developers designing the Bucharesti School database can ensure their work is ethically sound, beyond just implementing security measures.

Developers of a school database can ensure ethical design by implementing transparent data collection policies, gaining consent from stakeholders, and ensuring data is not inappropriately shared or used to third parties without consent.

Outline why the OlymRec attribute must have a data type that supports decimals. Why can't it be an integer?

<p>The value in <code>OlymRec</code> has a decimal point; therefore, an accurate data type that supports storing numbers with decimal places is required.</p> Signup and view all the answers

Why is it important to normalize databases from 2NF (Second Normal Form) to 3NF (Third Normal Form)?

<p>To remove transitive non-key dependencies, where non-key attributes depend on another non-key attribute and further reduce data redundancy.</p> Signup and view all the answers

Explain the importance of choosing the correct data type for the 'Gradient' attribute in the plant database.

<p>Choosing the correct data type, like integer, ensures data integrity and allows for accurate calculations and comparisons, which are essential for analyzing environmental gradients. Also avoids errors and ensures compatibility with analysis tools.</p> Signup and view all the answers

Describe a scenario where data validation on the 'Gradient' attribute would prevent incorrect data entry, and explain the consequences of not implementing this validation.

<p>If a user enters a gradient value of '1000', data validation (e.g., a range check) would flag this as an error because gradients are expected to be within -90 to +90 degrees. Without validation, this incorrect value could skew statistical analyses and lead to false conclusions about environmental impacts on plant distribution.</p> Signup and view all the answers

Explain how the relationship described in the entity relationship diagram (ERD) between 'PLANT', 'Distribution', and 'Site' ensures data integrity and prevents orphaned records.

<p>The relationships ensure that each plant record is associated with valid distribution and site records. This prevents having plant records without location data, or distribution entries that do not correspond to an actual plant or site. Referential integrity ensures that no orphaned records exist.</p> Signup and view all the answers

Why is a composite primary key (Plant ID and Site ID) necessary for the Distribution table, and what problem would arise if only Plant ID was used as the primary key?

<p>A composite key is needed because a single plant can be present at multiple sites, and a single site can contain multiple plants; therefore, PlantID alone cannot uniquely identify a record. If only Plant ID was used, there could be multiple sites listed for the same plant ID, violating primary key constraints.</p> Signup and view all the answers

The SQL query provided aims to find the number of sites where 'Gorse' was found on '14/10/2019'. Identify a potential issue with this query that could lead to inaccurate results, and suggest a modification to correct it.

<p>The query uses an implicit join (listing tables in the FROM clause and joining them in the WHERE clause), which can lead to unintended Cartesian products if the join condition is not specific enough.</p> <p>To correct it, use an explicit JOIN clause:</p> <pre><code class="language-sql">SELECT COUNT(DISTINCT SITE_ID) FROM PLANT JOIN Distribution ON PLANT.Plant_ID = Distribution.PlantID WHERE species = 'Gorse' AND DATE = '14/10/2019'; </code></pre> Signup and view all the answers

Describe how a Database Administrator (DBA) could ensure that the database remains available and performs optimally during peak usage times.

<p>A DBA can implement performance monitoring tools, optimize query performance by creating indexes, manage server resources to prevent bottlenecks, and plan for scalability by adding more server capacity or optimizing database configurations.</p> Signup and view all the answers

Explain how the DBMS ensures that the school bus payment transaction maintains ACID properties (Atomicity, Consistency, Isolation, Durability).

<p>The DBMS ensures Atomicity by treating the entire payment process as a single transaction: either all steps (authentication, bill calculation, payment processing, and account crediting) succeed, or none do. Consistency is ensured by applying validation rules and constraints to maintain data accuracy. Isolation prevents concurrent transactions from interfering with each other. Durability ensures that once the transaction is committed, the changes are permanently saved, even in the event of system failures.</p> Signup and view all the answers

Discuss how normalization contributes to data consistency in the environment database, and provide an example of a denormalized structure that would lead to data inconsistency.

<p>Normalization reduces redundancy by organizing data into multiple related tables, ensuring that each piece of information is stored only once. For example, species information is stored in a separate 'Species' table and linked via a 'Species ID' in other tables, avoiding duplication.</p> <p>A denormalized structure where species name, characteristics, and conservation status were all stored within the 'Plant' table would lead to inconsistency. Updating the conservation status of a widespread plant species would require updating multiple records in the 'Plant' table, increasing the risk of errors.</p> Signup and view all the answers

Flashcards

Database Administrator Roles

Controlling data access and implementing security measures to protect the database.

DBMS Security Measures

Limiting user access and encrypting sensitive data to prevent unauthorized viewing.

Ethical Database Design

Implementing privacy measures, transparent policies, and obtaining consent to avoid misuse.

Why Normalize Databases?

To minimize data duplication, saving storage space and improving data integrity.

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2NF to 3NF Normalization

To remove transitive dependencies, reducing redundancy even further.

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Data validation

Ensures data entered is within an appropriate range or format.

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Composite Primary Key

A key formed by combining two or more attributes to uniquely identify each record.

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Database Management System (DBMS)

Software for managing databases; examples can include user authentication, transaction processing and calculating bills/amounts.

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Record Locking

Limiting access while a record is being updated, preventing simultaneous changes.

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Data consistency

Ensures that data remains accurate and consistent throughout its lifecycle.

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Isolation (in DBMS)

Prevents data values from being accessed by a transaction while another transaction involving the same data is in progress.

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Normalization

Eliminates data redundancy by organizing information across multiple related tables, preventing data duplcation.

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Range checks

Checking that the values are within acceptable boundaries.

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Study Notes

Database Fundamentals

  • Data types include strings or text for species and integers for gradients.
  • Data validation for the gradient attribute involves checking if the entered data falls within an acceptable range (e.g., -90 to +90).
  • A composite primary key is used for the Distribution table because Plant ID and Site ID can be repeated, as many plants can be at one site, and many sites can have several plants.

Database Queries and Transactions

  • To calculate the total number of sites where gorse was found on 14 October 2019, use: SELECT COUNT(SITE_ID) FROM PLANT, Distribution WHERE species = "Gorse" AND DATE = "14/10/2019" AND PLANT.Plant-ID = Distribution.Plant-ID
  • When a parent pays the school bus at month's end:
  • The parent is authenticated by the DBMS.
  • The amount/bill is calculated and displayed.
  • A transaction is initiated for the transport payment.
  • Payment details are added for transport.
  • If payment details can be processed by the DBMS, the school transport account is credited.

Data Consistency

  • Data consistency can be maintained by using data validation, such as range checks for numerical values like gradient.
  • Referential integrity ensures that Species IDs in the plant table match valid records.
  • Normalization eliminates data redundancy by organizing information across multiple related tables.
  • Regular data updates and constraints prevent incorrect or duplicate entries.

Database Management System Roles and Features

  • A DBMS prevents simultaneous updates of a record by two parents through record locking, isolation, and data locking.
  • Exclusive editing is done in isolation to prevent data values from being accessed by another transaction involving the same data while one transaction is in progress.
  • Two roles of a database administrator include approving data access and implementing security.
  • A DBMS can ensure the security of students' personal data by using:
    • Access controls: effective and efficient access controls so that end users can access only the data or programs for which they have privileges.
    • Data encryption: ensure the confidentiality of data.

Ethical Database Design

  • Developers of a school database can ensure ethical design using measures such as strict data privacy measures such as encryption and access controls to protect student information.
  • Transparent data collection policies and obtaining consent from data subjects are essential.
  • Data is not shared inappropriate with third parties without the consent of the data subject.

Database Normalization

  • Databases are normalized to reduce duplicated or remove redundant data, which reduces wastage of storage space.
  • The Olympic Record attribute (OlymRec) cannot be an integer because its value has a decimal point, and an integer data type is required.
  • Databases are normalized from 2NF to 3NF to remove transitive non-key dependencies, where non-key attributes depend on another non-key attribute, and to further reduce data redundancy.

Normal Forms

  • 1NF: Unique PK, Athletics (EventID, Event, type, subtype, gender, OlymRec, WId Rec)
  • 2NF: Composite PK, Athletics (Events Type, Subtype, Gender, OlymRec, WId Rec), Events (Event, type, Subtype)
  • 3NF:
    • Athletics (Event, Gender, OlymRec, WIdRec)
    • EVENTS ( EventIID, Event, Type, subtype)
    • Athletics (EventID, gender, OlymRec, WIdRec

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Description

Explanation of data types (strings, integers) and validation, focusing on using acceptable ranges. Shows the usage of composite primary keys when attributes can be repeated. Includes a sample calculation for the total number of sites where gorse was found using SQL.

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