Database Design Concepts and ER Diagrams
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Questions and Answers

What is a derived attribute?

  • An attribute that is fixed and unchangeable
  • An attribute that cannot be calculated from other attributes
  • A type of attribute that exists independently
  • An attribute that is obtained from other attributes (correct)

    • Which of the following is an example of a derived attribute?

  • Age (correct)
  • Phone number
  • Name
  • Address

    • Why might a complex structure be necessary in data modeling?

  • To eliminate the concept of derived attributes
  • To minimize the attributes needed in the model
  • To represent data that has simple relationships
  • To manage data with multiple integrated parts (correct)

    • Which of the following statements is false regarding derived attributes?

    <p>They are always with fixed values. (C)</p> Signup and view all the answers

    What can be an example of data that requires a complex structure?

    <p>Phone number (B)</p> Signup and view all the answers

    What does a column in a data table primarily represent?

    <p>An attribute of an entity (B)</p> Signup and view all the answers

    What is the purpose of the entity name in a database table?

    <p>It translates to the name of the table (B)</p> Signup and view all the answers

    Which statement correctly describes how data is organized in a table?

    <p>Data is stored in rows and columns (A)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of a column in a data table?

    <p>It represents the entity's hierarchical structure (A)</p> Signup and view all the answers

    How are the contents of a data table structured?

    <p>Rows contain records for each entity (A)</p> Signup and view all the answers

    What is the primary purpose of grouping data in SQL?

    <p>To perform calculations across multiple records (D)</p> Signup and view all the answers

    Which of the following represents the correct element of a basic SQL SELECT statement with grouping?

    <p>SELECT * FROM table GROUP BY column1 (A)</p> Signup and view all the answers

    Which statement best represents an aggregate function that can be used after grouping?

    <p>COUNT() to count unique values (B)</p> Signup and view all the answers

    When using aggregate functions in a SQL query, which clause must be included after the WHERE clause?

    <p>GROUP BY (D)</p> Signup and view all the answers

    What should the SQL statement include to ensure that aggregate results are filtered appropriately?

    <p>Using the HAVING clause after GROUP BY (C)</p> Signup and view all the answers

    What is the primary purpose of the referencing keyword in a constraint?

    <p>To link two tables by matching data (B)</p> Signup and view all the answers

    What does establishing a reference between two tables with a constraint ensure?

    <p>The data in a column matches an existing value in the referenced table (A)</p> Signup and view all the answers

    Which of the following is NOT a function of the referencing keyword in database constraints?

    <p>Ensuring data types are compatible (B)</p> Signup and view all the answers

    When using referencing in constraints, what must be true for the data in the referencing table?

    <p>It must match an existing value in the referenced table (D)</p> Signup and view all the answers

    Which statement accurately describes the relationship created by the referencing keyword?

    <p>It creates a one-to-many relationship between related tables (D)</p> Signup and view all the answers

    What does the command SELECT * FROM student WHERE GPA BETWEEN 70 AND 75; achieve?

    <p>Retrieves all rows from <code>student</code> where GPA is between 70 and 75 inclusive (A)</p> Signup and view all the answers

    Which part of the SQL command specifies the range of GPA values to filter?

    <p>WHERE GPA BETWEEN 70 AND 75 (A)</p> Signup and view all the answers

    What would happen if the command was modified to SELECT * FROM student WHERE GPA BETWEEN 70 AND 75 OR GPA = 80;?

    <p>It retrieves all students with GPA values of either 70 to 75 or exactly 80 (D)</p> Signup and view all the answers

    Why is the keyword 'BETWEEN' used instead of the more general '>=' and '<=' in the command?

    <p>It simplifies the syntax and makes the query easier to read (A)</p> Signup and view all the answers

    If the command is executed and there are no students with a GPA between 70 and 75, what will be the result?

    <p>No rows will be returned from the query (C)</p> Signup and view all the answers

    What does the SQL command SELECT fname, city, salary FROM person WHERE city = 'Irbid'; retrieve?

    <p>The <code>fname</code>, <code>salary</code>, and <code>city</code> of individuals from <code>'Irbid'</code> (A)</p> Signup and view all the answers

    Which part of the SQL command specifies the condition for which rows to return?

    <p>WHERE city = 'Irbid' (D)</p> Signup and view all the answers

    If the FROM clause is missing from the SQL command, what will happen?

    <p>An error will occur due to invalid syntax (B)</p> Signup and view all the answers

    What type of data structure is being referenced with the term person in the SQL command?

    <p>A table in a database (A)</p> Signup and view all the answers

    If the condition in the WHERE clause was changed to WHERE city = 'Amman', what would be the outcome?

    <p>The command will now retrieve data for individuals located in <code>'Amman'</code> (D)</p> Signup and view all the answers

    Flashcards

    String

    A data type that represents a sequence of characters.

    Derived Attribute

    A characteristic that is calculated or derived from other attributes in the data.

    Atomic Attribute

    An attribute that cannot be broken down into smaller parts.

    Composite Attribute

    A data structure used to represent complex data that has multiple parts.

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    Phone Number

    A data type that represents a phone number.

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    Data

    The information stored in a table. It is organized in rows and columns.

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    Column

    A column in a table that represents an attribute of an entity. Example: In a "Customers" table, "Name" and "Address" are commonly used columns.

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    Attribute

    An attribute in a table, describing an entity.

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    Entity Name

    Represents the name of a table in a database.

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    Entity

    A collection of data about a particular subject.

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    SELECT Statement

    A command used to retrieve data from a database.

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    SELECT Clause

    Specifies the columns you want to retrieve from the table.

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    FROM Clause

    The table from which data will be retrieved.

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    WHERE Clause

    Used to filter the data based on specific conditions.

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    Condition

    A value used in the WHERE clause to filter data.

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    referencing

    A keyword used in database constraints to connect two tables.

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    referencing constraint

    A constraint that enforces data integrity by ensuring a column's values exist in another table.

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    referenced column

    A column that contains values that must match existing values in a referenced table.

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    referenced table

    The table that contains the values that are referenced in another table.

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    referencing constraint purpose

    Ensures data consistency and prevents invalid entries by checking for matching values in a reference table.

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    SELECT command

    The SELECT command retrieves data from a database table.

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    SELECT *

    The * symbol is used to select all columns from a table.

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    BETWEEN operator

    The BETWEEN operator selects values within a specified range, inclusive.

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    Aggregate Function

    A function that operates on a set of values to produce a single result, like finding the average or sum.

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    Grouping

    A process of dividing data into groups based on common characteristics.

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    SELECT Statement with Aggregate Functions

    A SQL statement used to calculate aggregate values for each group created by the GROUP BY clause.

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    GROUP BY Clause

    A clause used in SQL to group rows with the same value in one or more columns.

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    Columns in SELECT Statement

    The columns used in a SELECT statement when applying aggregate functions. Typically, they represent the columns used for grouping.

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    Study Notes

    Database Design

    • Database design involves analysis, entity-relationship diagrams (ER-diagrams), schema design (DDL), and data manipulation (DML).
    • Analysis focuses on identifying entities, attributes, and relationships between them.
    • Entities represent objects or concepts (e.g., Student, Course).
    • Attributes describe characteristics of entities (e.g., student name, course name).
    • Relationships depict connections between entities (e.g., student takes courses).

    Entity Relationship Diagrams (ER diagrams)

    • ER diagrams visually represent the entities, attributes, and relationships in a database.
    • Key attributes: unique identifiers for entities (e.g., student ID). These help identify and distinguish one entity from another
    • Composite attributes: attributes that consist of multiple smaller attributes (e.g., an address has city, street, etc.).
    • Multi-valued attributes: attributes that can hold multiple values for an entity (e.g., phone numbers for a student).
    • Derived attributes: attributes that can be calculated from other attributes (e.g., age from date of birth).

    Relationships

    • Cardinality ratio defines the number of entities in one entity set that can be related to an entity in another entity set. Cardinality ratios are 1:1, 1:M, or M:N (sometimes written as M:M).
    • Participation constraint: total or partial participation of an entity in a relationship indicates whether every entity takes part in the relationship (total) or if some entities can be excluded from a specific relationship (partial). The cardinality ratio and participation constraint work together to dictate how entities map during schema design

    Entity Types

    • Strong entities exist independently and have a unique primary key.
    • Weak entities depend on a strong entity and don't have their own primary key. The primary key of the weak entity includes at least one identifying attribute from the related strong entity.

    Database Management Systems (DBMS)

    • DBMS is software that manages databases.
    • SQL Server is a popular relational database system.
    • SQL is a structured query language used to interact with relational databases.
    • DDL (Data Definition Language): used to create, modify, and delete databases and tables. Common commands include CREATE, DROP, ALTER.
    • DML (Data Manipulation Language): used to insert, retrieve, and update data in tables. Common commands include INSERT, SELECT, UPDATE, DELETE.

    Constraints

    • Constraints define rules and restrictions on data in a table.
    • Primary key: a unique identifier for each record in a table. Each table must have a primary key.
    • Foreign key: a field in one table that refers to the primary key of another table, creating a link between the two tables.
    • Unique: a constraint that enforces uniqueness of a column's values.
    • Not null: a constraint that enforces that a column cannot contain null values.
    • Check: a constraint that specifies a condition that values in a column must satisfy.
    • Default: a constraint that specifies a default value for a column if no other value is given.

    SQL Operations (DML)

    • SELECT: retrieve data from tables based on specified criteria (filtering rows and/or columns).
    • INSERT: add new data to a table.
    • UPDATE: modify existing data in a table.
    • DELETE: remove data from a table.

    SQL Functions (aggregate functions)

    • COUNT: calculates the number of rows in a table.
    • AVG: calculates the average of values in a column.
    • SUM: calculates the sum of values in a column.
    • MIN: finds the smallest value in a column.
    • MAX: finds the largest value in a column.
    • These aggregate function with the 'group by' clause are used to retrieve information about multiple groups of data rather than just the whole table

    SQL Clauses (additional features)

    • ORDER BY: sorts the retrieved data based on column values.
    • GROUP BY: groups rows that have the same values in specified columns.
    • HAVING: filters grouped rows based on conditions.
    • TOP/LIMIT specifies how many rows to return from the selected result.
    • LIKE: searches for patterns in column values (wildcards, e.g., % for any character sequence, _ for any single character).

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    Description

    This quiz covers the fundamentals of database design, including the analysis of entities and relationships, as well as the creation of entity-relationship diagrams (ER diagrams). Key concepts such as attributes, unique identifiers, and types of attributes are also explored. Test your understanding of how to design and represent data structures effectively.

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