Relational Databases: The Relational Model
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Questions and Answers

In the relational model, what is a table?

  • An unnamed tuple of values
  • An ordered collection of elements enclosed in parentheses
  • A fixed tuple of columns and a varying set of rows (correct)
  • An unordered collection of elements enclosed in braces

    • What are the data structures that prescribe how data is organized in a database model?

  • Tuples and sets
  • Tables and columns (correct)
  • Rows and columns
  • Data types and columns

    • What is the theoretical foundation of the SQL language?

  • Big data
  • Relational rules
  • Set theory
  • Relational algebra (correct)

    • What characterizes big data?

    <p>Unprecedented data volumes and rapidly changing data structures</p> Signup and view all the answers

    What is a data type in the context of databases?

    <p>A named set of values from which column values are drawn</p> Signup and view all the answers

    What does a row represent in a database table?

    <p>An unnamed tuple of values</p> Signup and view all the answers

    What do relational rules govern in a relational database?

    <p>Valid data</p> Signup and view all the answers

    What is the relational model based on?

    <p>Set theory</p> Signup and view all the answers

    Which language standardizes the data structure, operations, and rules in the relational model?

    <p>SQL</p> Signup and view all the answers

    What is a column in the context of a database table?

    <p>An unnamed tuple of values corresponding to a column</p> Signup and view all the answers

    In a CREATE TABLE statement, which keyword specifies the column values to be added?

    <p>VALUES</p> Signup and view all the answers

    What is the keyword used to modify existing rows in a table with the UPDATE statement?

    <p>SET</p> Signup and view all the answers

    Which keyword is used to ensure that a column or group of columns is always unique and non-null in a CREATE TABLE statement?

    <p>PRIMARY KEY</p> Signup and view all the answers

    What keyword follows the column's data type to define an auto-increment column in a CREATE TABLE statement?

    <p>AUTO_INCREMENT</p> Signup and view all the answers

    What is the term for a foreign key constraint added to a CREATE TABLE statement that refers to a primary key?

    <p>FOREIGN KEY</p> Signup and view all the answers

    Which action, specified in the ON UPDATE and ON DELETE clauses of a FOREIGN KEY constraint, propagates primary key changes to foreign keys?

    <p>CASCADE</p> Signup and view all the answers

    What type of constraint ensures that values in a column, or group of columns, are unique in a database?

    <p>UNIQUE</p> Signup and view all the answers

    In a CREATE TABLE statement, where does the CHECK constraint appear?

    <p>In a separate clause of the CREATE TABLE statement</p> Signup and view all the answers

    What is the term for a simple or composite foreign key in which all columns are NULL?

    <p>Fully NULL foreign key</p> Signup and view all the answers

    Which keyword is used to delete all rows from a table in a TRUNCATE statement?

    <p>TRUNCATE</p> Signup and view all the answers

    Which language is used for storing, manipulating, and retrieving data?

    <p>SQL</p> Signup and view all the answers

    What does the CREATE TABLE statement do?

    <p>Creates a new table</p> Signup and view all the answers

    What does the NULL value represent in a database?

    <p>A special value for unknown or inapplicable data</p> Signup and view all the answers

    Which type of constraint prevents a column from having a NULL value?

    <p>NOT NULL constraint</p> Signup and view all the answers

    What type of language is SQL?

    <p>High-level language</p> Signup and view all the answers

    What does the SELECT statement do?

    <p>Selects rows from a table to retrieve data</p> Signup and view all the answers

    What is the purpose of the LIMIT clause in MySQL?

    <p>Limits the number of rows returned in the result set</p> Signup and view all the answers

    What is the purpose of Data Definition Language (DDL) in databases?

    <p>Defining database structure</p> Signup and view all the answers

    What is meant by Data Independence?

    <p>The ability to modify the database schema without affecting the application programs</p> Signup and view all the answers

    What does the DROP DATABASE statement do?

    <p>Deletes a database and its contents</p> Signup and view all the answers

    Which keyword is used to prevent a column from having a NULL value in a CREATE TABLE statement?

    <p>NOT NULL</p> Signup and view all the answers

    What keyword follows the column's data type to define an auto-increment column in a CREATE TABLE statement?

    <p>AUTO_INCREMENT</p> Signup and view all the answers

    In a CREATE TABLE statement, where does the CHECK constraint appear?

    <p>In a separate clause of the CREATE TABLE statement</p> Signup and view all the answers

    Which keyword is used to delete all rows from a table in a TRUNCATE statement?

    <p>TRUNCATE</p> Signup and view all the answers

    What is the term for a simple or composite foreign key in which all columns are NULL?

    <p>Fully NULL foreign key</p> Signup and view all the answers

    What does the UNIQUE constraint ensure in a database?

    <p>Unique values in a column or group of columns</p> Signup and view all the answers

    Which keyword is used to modify existing rows in a table with the UPDATE statement?

    <p>SET</p> Signup and view all the answers

    What is the purpose of the RESTRICT keyword in the context of referential integrity?

    <p>Rejects insert, update, or delete that violates referential integrity</p> Signup and view all the answers

    'Referential integrity is a relational rule that requires foreign key values are either fully NULL or match some primary key value.' What keyword specifies this behavior?

    <p>RESTRICT</p> Signup and view all the answers

    What is the purpose of the Data Control Language (DCL) in a database system?

    <p>Controls user access</p> Signup and view all the answers

    Which type of language standardizes the data structure, operations, and rules in the relational model?

    <p>Data Definition Language (DDL)</p> Signup and view all the answers

    In the context of a database table, what does a row represent?

    <p>Unnamed values</p> Signup and view all the answers

    What keyword follows the column's data type to define an auto-increment column in a CREATE TABLE statement?

    <p>AUTO_INCREMENT</p> Signup and view all the answers

    Which action is specified in the ON UPDATE and ON DELETE clauses of a FOREIGN KEY constraint to propagate primary key changes to foreign keys?

    <p>CASCADE</p> Signup and view all the answers

    What is meant by Data Independence in the context of databases?

    <p>Allows changes in the physical storage of data without affecting the logical view</p> Signup and view all the answers

    What characterizes big data in the context of databases?

    <p>Large volume, velocity, and variety of data</p> Signup and view all the answers

    What does the IS NULL operator do in SQL?

    <p>Selects NULL values</p> Signup and view all the answers

    What does the DROP DATABASE statement do in SQL?

    <p>Deletes an existing database</p> Signup and view all the answers

    What is the purpose of the Limit clause in MySQL?

    <p>Limits the number of rows returned by a SQL query</p> Signup and view all the answers

    Which of the following best describes the relational model in database systems?

    <p>It is a database model based on a tabular data structure.</p> Signup and view all the answers

    What do relational rules govern in a relational database?

    <p>They govern the integrity and consistency of data within the database.</p> Signup and view all the answers

    What is the theoretical foundation of the SQL language?

    <p>Relational Algebra</p> Signup and view all the answers

    Which language standardizes the data structure, operations, and rules in the relational model?

    <p>SQL</p> Signup and view all the answers

    What characterizes big data?

    <p>It is characterized by unprecedented data volumes and rapidly changing data structures.</p> Signup and view all the answers

    What is meant by Data Independence in the context of databases?

    <p>It refers to the ability to modify data without affecting the programs that access the data.</p> Signup and view all the answers

    What does the DROP DATABASE statement do?

    <p>It removes an entire database and all its objects from the server.</p> Signup and view all the answers

    What is the primary data structure in the relational model?

    <p>Relational</p> Signup and view all the answers

    Which database system is known for its integration with object-oriented programming languages?

    <p>Neo4j</p> Signup and view all the answers

    What theoretical foundation is the relational data structure based on?

    <p>Set theory</p> Signup and view all the answers

    Which database system is known for its flexibility in handling unstructured and semi-structured data?

    <p>MongoDB</p> Signup and view all the answers

    Which type of constraint ensures that a column or group of columns in a table is always unique and non-null?

    <p>UNIQUE</p> Signup and view all the answers

    What is the purpose of the CHECK constraint in a database table?

    <p>To specify conditions for column values</p> Signup and view all the answers

    What is the purpose of the TRUNCATE statement in SQL?

    <p>To delete all rows from a table</p> Signup and view all the answers

    In the context of a database, what does the term 'NULL' represent?

    <p>Missing data</p> Signup and view all the answers

    What happens when a column is assigned the NOT NULL constraint in a database table?

    <p>The column cannot have a NULL value</p> Signup and view all the answers

    What is the purpose of the SELECT statement in SQL?

    <p>To retrieve data from a table</p> Signup and view all the answers

    What is the purpose of the INSERT statement in SQL?

    <p>To add new rows to a table</p> Signup and view all the answers

    Which statement is used to modify existing rows in a table in SQL?

    <p>UPDATE</p> Signup and view all the answers

    'Expressions' in SQL consist of which of the following components?

    <p>Operators, operands, and parentheses</p> Signup and view all the answers

    What does the SELECT clause specify in SQL?

    <p>Expressions to return values for each row</p> Signup and view all the answers

    Which statement deletes specific rows from a table based on specified criteria in SQL?

    <p>DELETE</p> Signup and view all the answers

    What does a primary key constraint ensure in SQL?

    <p>Columns are unique and non-null</p> Signup and view all the answers

    Which statement is used to delete an existing table and all its data in a SQL database?

    <p>DROP TABLE</p> Signup and view all the answers

    Which data type stores raw binary data in a relational database?

    <p>BINARY</p> Signup and view all the answers

    What keyword specifies the behavior that foreign key values are either fully NULL or match some primary key value in referential integrity?

    <p>RESTRICT</p> Signup and view all the answers

    Which clause of the ALTER TABLE statement is used to add new columns to an existing table in a SQL database?

    <p>ADD COLUMN</p> Signup and view all the answers

    Which data type is used for storing geometric information in a relational database?

    <p>POINT</p> Signup and view all the answers

    What does the modulo operator (%) do in SQL?

    <p>Returns the remainder of a division</p> Signup and view all the answers

    Which statement is used to select specific rows from tables based on various conditions in SQL?

    <p>SELECT TABLE</p> Signup and view all the answers

    .What does the IS NULL operator do in SQL?

    <p>Returns true if a value is NULL</p> Signup and view all the answers

    Which keyword follows the column's data type to define an auto-increment column in a CREATE TABLE statement?

    <p>AUTO_INCREMENT</p> Signup and view all the answers

    Which action, specified in the ON UPDATE and ON DELETE clauses of a FOREIGN KEY constraint, propagates primary key changes to foreign keys?

    <p>CASCADE</p> Signup and view all the answers

    Which type of constraint prevents a column from having a NULL value?

    <p>Check constraint</p> Signup and view all the answers

    What does the CREATE TABLE statement do?

    <p>Defines a new table and its columns</p> Signup and view all the answers

    What characterizes big data in the context of databases?

    <p>Data with volume, velocity, and variety</p> Signup and view all the answers

    What is the purpose of the RESTRICT keyword in the context of referential integrity?

    <p>To prevent delete or update operations if they would violate referential integrity</p> Signup and view all the answers

    What does the IS NULL operator do in SQL?

    <p>Checks if a value is NULL</p> Signup and view all the answers

    What is the purpose of Data Definition Language (DDL) in databases?

    <p>To define and modify the structure of the database</p> Signup and view all the answers

    What characterizes big data?

    <p>It has high volume, velocity, and variety</p> Signup and view all the answers

    'Referential integrity is a relational rule that requires foreign key values are either fully NULL or match some primary key value.' What keyword specifies this behavior?

    <p>ON DELETE SET NULL</p> Signup and view all the answers

    'In the context of a database table, what does a row represent?'

    <p>A single record or tuple</p> Signup and view all the answers

    Which language standardizes the data structure, operations, and rules in the relational model?

    <p>Structured Query Language (SQL)</p> Signup and view all the answers

    What is the term for a simple or composite foreign key in which all columns are NULL?

    <p>Weak foreign key</p> Signup and view all the answers

    What keyword follows the column's data type to define an auto-increment column in a CREATE TABLE statement?

    <p>AUTO_INCREMENT</p> Signup and view all the answers

    Which keyword is used to specify the column values to be added in a CREATE TABLE statement?

    <p>VALUES</p> Signup and view all the answers

    What characterizes big data in the context of databases?

    <p>Data with velocity, variety, and volume</p> Signup and view all the answers

    What is the purpose of the Data Control Language (DCL) in a database system?

    <p>Enforce data integrity and security</p> Signup and view all the answers

    In a CREATE TABLE statement, where does the CHECK constraint appear?

    <p>After the column name and data type</p> Signup and view all the answers

    What do relational rules govern in a relational database?

    <p>Referential integrity constraints</p> Signup and view all the answers

    What is the term for a foreign key constraint added to a CREATE TABLE statement that refers to a primary key?

    <p>Referential key</p> Signup and view all the answers

    What does the IS NULL operator do in SQL?

    <p>Checks if a value is NULL</p> Signup and view all the answers

    What is meant by Data Independence in the context of databases?

    <p>The ability to modify data without impacting applications using that data</p> Signup and view all the answers

    What does the SELECT statement do?

    <p>Retrieves data from one or more tables</p> Signup and view all the answers

    What characterizes big data in the context of databases?

    <p>Data with velocity, variety, and volume</p> Signup and view all the answers

    Which keyword is used to prevent a column from having a NULL value in a CREATE TABLE statement?

    <p>NOT NULL</p> Signup and view all the answers

    What is the purpose of Data Definition Language (DDL) in databases?

    <p>Define database structure and schema</p> Signup and view all the answers

    Study Notes

    • Business rules are specific to a database and based on business policy.

    • Constraints are rules implemented as SQL constraints enforced by the database system.

    • SQL is a high-level language used for storing, manipulating, and retrieving data.

    • SQL statement is a complete command composed of one or more clauses, e.g. SELECT, FROM, and WHERE.

    • Data Definition Language (DDL) defines database structure, Data Query Language (DQL) retrieves data, Data Manipulation Language (DML) manipulates data, Data Control Language (DCL) controls user access, and Data Transaction Language (DTL) manages transactions.

    • Database system instance: a single executing copy of a database system, e.g., personal computers run one instance, shared computers run multiple instances.

    • Creating a new database: CREATE DATABASE DatabaseName, deleting a database: DROP DATABASE DatabaseName, selecting a default database: USE DatabaseName.

    • Tables: have a name, sequence of columns, and varying set of rows. Columns have a name and data type, rows have unnamed values, cells are single column-single row, empty table is a table without rows.

    • Data independence: Rule 4, CREATE TABLE creates a new table, DROP TABLE deletes a table and its rows, ALTER TABLE modifies columns.

    • Data types include: Integer, Decimal, Character, Date and time, Binary, Spatial, Document, Signed, and Unsigned.

    • Operators: Arithmetic, Comparison, Logical, Unary, and Binary. Expressions evaluate to a single value.

    • SELECT statement: selects rows from a table, has a SELECT and FROM clause, returns a result table.

    • Limiting the number of rows: MySQL's LIMIT clause.

    • NULL: a special value for unknown or inapplicable data.

    • NOT NULL constraint: prevents a column from having a NULL value.

    • IS NULL and IS NOT NULL operators: used to select NULL values.

    • Business rules are specific to a database and based on business policy.

    • Constraints are rules implemented as SQL constraints enforced by the database system.

    • SQL is a high-level language used for storing, manipulating, and retrieving data.

    • SQL statement is a complete command composed of one or more clauses, e.g. SELECT, FROM, and WHERE.

    • Data Definition Language (DDL) defines database structure, Data Query Language (DQL) retrieves data, Data Manipulation Language (DML) manipulates data, Data Control Language (DCL) controls user access, and Data Transaction Language (DTL) manages transactions.

    • Database system instance: a single executing copy of a database system, e.g., personal computers run one instance, shared computers run multiple instances.

    • Creating a new database: CREATE DATABASE DatabaseName, deleting a database: DROP DATABASE DatabaseName, selecting a default database: USE DatabaseName.

    • Tables: have a name, sequence of columns, and varying set of rows. Columns have a name and data type, rows have unnamed values, cells are single column-single row, empty table is a table without rows.

    • Data independence: Rule 4, CREATE TABLE creates a new table, DROP TABLE deletes a table and its rows, ALTER TABLE modifies columns.

    • Data types include: Integer, Decimal, Character, Date and time, Binary, Spatial, Document, Signed, and Unsigned.

    • Operators: Arithmetic, Comparison, Logical, Unary, and Binary. Expressions evaluate to a single value.

    • SELECT statement: selects rows from a table, has a SELECT and FROM clause, returns a result table.

    • Limiting the number of rows: MySQL's LIMIT clause.

    • NULL: a special value for unknown or inapplicable data.

    • NOT NULL constraint: prevents a column from having a NULL value.

    • IS NULL and IS NOT NULL operators: used to select NULL values.

    • An auto-increment column is a column that automatically receives a new value when a new row is added. It is defined using the AUTO_INCREMENT keyword in a CREATE TABLE statement.

    • Auto-increment errors: MySQL allows inserting a specific value to an auto-increment column, but overriding the auto-increment for a primary key is generally a mistake.

    • A foreign key is a column or group of columns that refers to a primary key. Data types must match, but names do not have to. Foreign keys can be NULL or repeat values. They follow the referential integrity rule.

    • Multiple foreign keys can refer to the same primary key, and a foreign key can refer to a primary key in the same table.

    • A foreign key constraint is added to a CREATE TABLE statement with the FOREIGN KEY and REFERENCES keywords. It enforces referential integrity.

    • Referential integrity rules state that referencing key values must be NULL or match the primary key value.

    • Referential integrity violations can occur in four ways: a primary key is updated, a foreign key is updated, a primary key row is deleted, or a foreign key row is inserted.

    • When an insert, update, or delete statement violates referential integrity, databases can automatically correct it using one of four actions: RESTRICT, SET NULL, SET DEFAULT, or CASCADE.

    • ON UPDATE and ON DELETE clauses of the FOREIGN KEY constraint specify the action taken when a primary key is updated or deleted.

    • Column constraints govern values in a single column and are added after the column name and data type. Table constraints govern values in one or more columns and are added in a separate clause. The UNIQUE constraint ensures unique values in a column or group of columns. The CHECK constraint specifies an expression on one or more columns.

    • Constraints can be added and dropped using the ALTER TABLE statement.

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