Podcast
Questions and Answers
In the relational model, what is a table?
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?
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?
What is the theoretical foundation of the SQL language?
- Big data
- Relational rules
- Set theory
- Relational algebra (correct)
What characterizes big data?
What characterizes big data?
What is a data type in the context of databases?
What is a data type in the context of databases?
What does a row represent in a database table?
What does a row represent in a database table?
What do relational rules govern in a relational database?
What do relational rules govern in a relational database?
What is the relational model based on?
What is the relational model based on?
Which language standardizes the data structure, operations, and rules in the relational model?
Which language standardizes the data structure, operations, and rules in the relational model?
What is a column in the context of a database table?
What is a column in the context of a database table?
In a CREATE TABLE statement, which keyword specifies the column values to be added?
In a CREATE TABLE statement, which keyword specifies the column values to be added?
What is the keyword used to modify existing rows in a table with the UPDATE statement?
What is the keyword used to modify existing rows in a table with the UPDATE statement?
Which keyword is used to ensure that a column or group of columns is always unique and non-null in a CREATE TABLE statement?
Which keyword is used to ensure that a column or group of columns is always unique and non-null in a CREATE TABLE statement?
What keyword follows the column's data type to define an auto-increment column in a CREATE TABLE statement?
What keyword follows the column's data type to define an auto-increment column in a CREATE TABLE statement?
What is the term for a foreign key constraint added to a CREATE TABLE statement that refers to a primary key?
What is the term for a foreign key constraint added to a CREATE TABLE statement that refers to a primary key?
Which action, specified in the ON UPDATE and ON DELETE clauses of a FOREIGN KEY constraint, propagates primary key changes to foreign keys?
Which action, specified in the ON UPDATE and ON DELETE clauses of a FOREIGN KEY constraint, propagates primary key changes to foreign keys?
What type of constraint ensures that values in a column, or group of columns, are unique in a database?
What type of constraint ensures that values in a column, or group of columns, are unique in a database?
In a CREATE TABLE statement, where does the CHECK constraint appear?
In a CREATE TABLE statement, where does the CHECK constraint appear?
What is the term for a simple or composite foreign key in which all columns are NULL?
What is the term for a simple or composite foreign key in which all columns are NULL?
Which keyword is used to delete all rows from a table in a TRUNCATE statement?
Which keyword is used to delete all rows from a table in a TRUNCATE statement?
Which language is used for storing, manipulating, and retrieving data?
Which language is used for storing, manipulating, and retrieving data?
What does the CREATE TABLE statement do?
What does the CREATE TABLE statement do?
What does the NULL value represent in a database?
What does the NULL value represent in a database?
Which type of constraint prevents a column from having a NULL value?
Which type of constraint prevents a column from having a NULL value?
What type of language is SQL?
What type of language is SQL?
What does the SELECT statement do?
What does the SELECT statement do?
What is the purpose of the LIMIT clause in MySQL?
What is the purpose of the LIMIT clause in MySQL?
What is the purpose of Data Definition Language (DDL) in databases?
What is the purpose of Data Definition Language (DDL) in databases?
What is meant by Data Independence?
What is meant by Data Independence?
What does the DROP DATABASE statement do?
What does the DROP DATABASE statement do?
Which keyword is used to prevent a column from having a NULL value in a CREATE TABLE statement?
Which keyword is used to prevent a column from having a NULL value in a CREATE TABLE statement?
What keyword follows the column's data type to define an auto-increment column in a CREATE TABLE statement?
What keyword follows the column's data type to define an auto-increment column in a CREATE TABLE statement?
In a CREATE TABLE statement, where does the CHECK constraint appear?
In a CREATE TABLE statement, where does the CHECK constraint appear?
Which keyword is used to delete all rows from a table in a TRUNCATE statement?
Which keyword is used to delete all rows from a table in a TRUNCATE statement?
What is the term for a simple or composite foreign key in which all columns are NULL?
What is the term for a simple or composite foreign key in which all columns are NULL?
What does the UNIQUE constraint ensure in a database?
What does the UNIQUE constraint ensure in a database?
Which keyword is used to modify existing rows in a table with the UPDATE statement?
Which keyword is used to modify existing rows in a table with the UPDATE statement?
What is the purpose of the RESTRICT keyword in the context of referential integrity?
What is the purpose of the RESTRICT keyword in the context of referential integrity?
'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?
'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?
What is the purpose of the Data Control Language (DCL) in a database system?
What is the purpose of the Data Control Language (DCL) in a database system?
Which type of language standardizes the data structure, operations, and rules in the relational model?
Which type of language standardizes the data structure, operations, and rules in the relational model?
In the context of a database table, what does a row represent?
In the context of a database table, what does a row represent?
What keyword follows the column's data type to define an auto-increment column in a CREATE TABLE statement?
What keyword follows the column's data type to define an auto-increment column in a CREATE TABLE statement?
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?
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?
What is meant by Data Independence in the context of databases?
What is meant by Data Independence in the context of databases?
What characterizes big data in the context of databases?
What characterizes big data in the context of databases?
What does the IS NULL operator do in SQL?
What does the IS NULL operator do in SQL?
What does the DROP DATABASE statement do in SQL?
What does the DROP DATABASE statement do in SQL?
What is the purpose of the Limit clause in MySQL?
What is the purpose of the Limit clause in MySQL?
Which of the following best describes the relational model in database systems?
Which of the following best describes the relational model in database systems?
What do relational rules govern in a relational database?
What do relational rules govern in a relational database?
What is the theoretical foundation of the SQL language?
What is the theoretical foundation of the SQL language?
Which language standardizes the data structure, operations, and rules in the relational model?
Which language standardizes the data structure, operations, and rules in the relational model?
What characterizes big data?
What characterizes big data?
What is meant by Data Independence in the context of databases?
What is meant by Data Independence in the context of databases?
What does the DROP DATABASE statement do?
What does the DROP DATABASE statement do?
What is the primary data structure in the relational model?
What is the primary data structure in the relational model?
Which database system is known for its integration with object-oriented programming languages?
Which database system is known for its integration with object-oriented programming languages?
What theoretical foundation is the relational data structure based on?
What theoretical foundation is the relational data structure based on?
Which database system is known for its flexibility in handling unstructured and semi-structured data?
Which database system is known for its flexibility in handling unstructured and semi-structured data?
Which type of constraint ensures that a column or group of columns in a table is always unique and non-null?
Which type of constraint ensures that a column or group of columns in a table is always unique and non-null?
What is the purpose of the CHECK constraint in a database table?
What is the purpose of the CHECK constraint in a database table?
What is the purpose of the TRUNCATE statement in SQL?
What is the purpose of the TRUNCATE statement in SQL?
In the context of a database, what does the term 'NULL' represent?
In the context of a database, what does the term 'NULL' represent?
What happens when a column is assigned the NOT NULL constraint in a database table?
What happens when a column is assigned the NOT NULL constraint in a database table?
What is the purpose of the SELECT statement in SQL?
What is the purpose of the SELECT statement in SQL?
What is the purpose of the INSERT statement in SQL?
What is the purpose of the INSERT statement in SQL?
Which statement is used to modify existing rows in a table in SQL?
Which statement is used to modify existing rows in a table in SQL?
'Expressions' in SQL consist of which of the following components?
'Expressions' in SQL consist of which of the following components?
What does the SELECT clause specify in SQL?
What does the SELECT clause specify in SQL?
Which statement deletes specific rows from a table based on specified criteria in SQL?
Which statement deletes specific rows from a table based on specified criteria in SQL?
What does a primary key constraint ensure in SQL?
What does a primary key constraint ensure in SQL?
Which statement is used to delete an existing table and all its data in a SQL database?
Which statement is used to delete an existing table and all its data in a SQL database?
Which data type stores raw binary data in a relational database?
Which data type stores raw binary data in a relational database?
What keyword specifies the behavior that foreign key values are either fully NULL or match some primary key value in referential integrity?
What keyword specifies the behavior that foreign key values are either fully NULL or match some primary key value in referential integrity?
Which clause of the ALTER TABLE statement is used to add new columns to an existing table in a SQL database?
Which clause of the ALTER TABLE statement is used to add new columns to an existing table in a SQL database?
Which data type is used for storing geometric information in a relational database?
Which data type is used for storing geometric information in a relational database?
What does the modulo operator (%) do in SQL?
What does the modulo operator (%) do in SQL?
Which statement is used to select specific rows from tables based on various conditions in SQL?
Which statement is used to select specific rows from tables based on various conditions in SQL?
.What does the IS NULL operator do in SQL?
.What does the IS NULL operator do in SQL?
Which keyword follows the column's data type to define an auto-increment column in a CREATE TABLE statement?
Which keyword follows the column's data type to define an auto-increment column in a CREATE TABLE statement?
Which action, specified in the ON UPDATE and ON DELETE clauses of a FOREIGN KEY constraint, propagates primary key changes to foreign keys?
Which action, specified in the ON UPDATE and ON DELETE clauses of a FOREIGN KEY constraint, propagates primary key changes to foreign keys?
Which type of constraint prevents a column from having a NULL value?
Which type of constraint prevents a column from having a NULL value?
What does the CREATE TABLE statement do?
What does the CREATE TABLE statement do?
What characterizes big data in the context of databases?
What characterizes big data in the context of databases?
What is the purpose of the RESTRICT keyword in the context of referential integrity?
What is the purpose of the RESTRICT keyword in the context of referential integrity?
What does the IS NULL operator do in SQL?
What does the IS NULL operator do in SQL?
What is the purpose of Data Definition Language (DDL) in databases?
What is the purpose of Data Definition Language (DDL) in databases?
What characterizes big data?
What characterizes big data?
'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?
'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?
'In the context of a database table, what does a row represent?'
'In the context of a database table, what does a row represent?'
Which language standardizes the data structure, operations, and rules in the relational model?
Which language standardizes the data structure, operations, and rules in the relational model?
What is the term for a simple or composite foreign key in which all columns are NULL?
What is the term for a simple or composite foreign key in which all columns are NULL?
What keyword follows the column's data type to define an auto-increment column in a CREATE TABLE statement?
What keyword follows the column's data type to define an auto-increment column in a CREATE TABLE statement?
Which keyword is used to specify the column values to be added in a CREATE TABLE statement?
Which keyword is used to specify the column values to be added in a CREATE TABLE statement?
What characterizes big data in the context of databases?
What characterizes big data in the context of databases?
What is the purpose of the Data Control Language (DCL) in a database system?
What is the purpose of the Data Control Language (DCL) in a database system?
In a CREATE TABLE statement, where does the CHECK constraint appear?
In a CREATE TABLE statement, where does the CHECK constraint appear?
What do relational rules govern in a relational database?
What do relational rules govern in a relational database?
What is the term for a foreign key constraint added to a CREATE TABLE statement that refers to a primary key?
What is the term for a foreign key constraint added to a CREATE TABLE statement that refers to a primary key?
What does the IS NULL operator do in SQL?
What does the IS NULL operator do in SQL?
What is meant by Data Independence in the context of databases?
What is meant by Data Independence in the context of databases?
What does the SELECT statement do?
What does the SELECT statement do?
What characterizes big data in the context of databases?
What characterizes big data in the context of databases?
Which keyword is used to prevent a column from having a NULL value in a CREATE TABLE statement?
Which keyword is used to prevent a column from having a NULL value in a CREATE TABLE statement?
What is the purpose of Data Definition Language (DDL) in databases?
What is the purpose of Data Definition Language (DDL) in databases?
Study Notes
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Business rules are specific to a database and based on business policy.
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Constraints are rules implemented as SQL constraints enforced by the database system.
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SQL is a high-level language used for storing, manipulating, and retrieving data.
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SQL statement is a complete command composed of one or more clauses, e.g. SELECT, FROM, and WHERE.
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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.
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Database system instance: a single executing copy of a database system, e.g., personal computers run one instance, shared computers run multiple instances.
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Creating a new database: CREATE DATABASE DatabaseName, deleting a database: DROP DATABASE DatabaseName, selecting a default database: USE DatabaseName.
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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.
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Data independence: Rule 4, CREATE TABLE creates a new table, DROP TABLE deletes a table and its rows, ALTER TABLE modifies columns.
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Data types include: Integer, Decimal, Character, Date and time, Binary, Spatial, Document, Signed, and Unsigned.
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Operators: Arithmetic, Comparison, Logical, Unary, and Binary. Expressions evaluate to a single value.
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SELECT statement: selects rows from a table, has a SELECT and FROM clause, returns a result table.
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Limiting the number of rows: MySQL's LIMIT clause.
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NULL: a special value for unknown or inapplicable data.
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NOT NULL constraint: prevents a column from having a NULL value.
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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.
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IS NULL and IS NOT NULL operators: used to select NULL values.
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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.
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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.
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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.
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Multiple foreign keys can refer to the same primary key, and a foreign key can refer to a primary key in the same table.
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A foreign key constraint is added to a CREATE TABLE statement with the FOREIGN KEY and REFERENCES keywords. It enforces referential integrity.
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Referential integrity rules state that referencing key values must be NULL or match the primary key value.
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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.
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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.
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ON UPDATE and ON DELETE clauses of the FOREIGN KEY constraint specify the action taken when a primary key is updated or deleted.
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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.
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Constraints can be added and dropped using the ALTER TABLE statement.
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Description
Learn about the relational model, a database model based on tabular data structure, published in 1970 by E. F. Codd of IBM and released in commercial products around 1980. Explore the data structures, operations, and rules governing valid data in the relational model.
