SQL Data Definition and Data Types

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Questions and Answers

Which data type is NOT considered a numeric data type in SQL?

FLOAT

VARCHAR(n) (correct)

DOUBLE PRECISION

SMALLINT

What does the DATE data type in SQL represent?

A string representing a date

Unique identifier for records

Numeric representation of the date

Year, Month, and Day in the format YYYY-MM-DD (correct)

Which of the following is a characteristic of a Boolean data type in SQL?

Stores varying length character strings

Represents values such as 1 and 0

Can store multiple integer values

Can only take on TRUE, FALSE, or NULL (correct)

Which command is used to create virtual relations in SQL?

CREATE VIEW Signup and view all the answers

What is a distinguishing feature of the TIMESTAMP data type?

It includes a time component. Signup and view all the answers

What is the primary purpose of the CREATE statement in SQL?

To define data structure and constraints Signup and view all the answers

In SQL, what comprises a schema?

Tables, constraints, views, domains, and other constructs Signup and view all the answers

Which SQL command would you use to create a new table?

CREATE TABLE Signup and view all the answers

What does the semicolon signify in SQL statements?

Ending of a statement Signup and view all the answers

Which of the following is NOT a component of an SQL schema?

Functions Signup and view all the answers

What is meant by 'DDL' in the context of SQL?

Data Definition Language Signup and view all the answers

Which SQL command is used to specify constraints on data?

CREATE TABLE Signup and view all the answers

What does a catalog in SQL contain?

A collection of schemas Signup and view all the answers

What does the INTERVAL data type in SQL specify?

A relative value for date manipulation Signup and view all the answers

What can cause errors when specifying foreign keys in a SQL table?

Referencing non-existent tables Signup and view all the answers

Which SQL command is used to define the data type for multiple attributes easily?

CREATE DOMAIN Signup and view all the answers

What does the CHECK clause specify in SQL?

Restrictions for individual tuples Signup and view all the answers

What is the purpose of the PRIMARY KEY clause in SQL?

To identify one or more attributes uniquely Signup and view all the answers

What happens when a FOREIGN KEY constraint is violated by default?

The update is ignored and no changes are made Signup and view all the answers

What is the function of the UNIQUE clause in SQL?

To specify a secondary key for a relation Signup and view all the answers

How can constraints be named in SQL?

By using the CONSTRAINT keyword Signup and view all the answers

What type of value does the NOT NULL constraint ensure for an attribute?

The attribute must not be left empty Signup and view all the answers

What does the SET DEFAULT action specify in a FOREIGN KEY constraint?

To assign a predefined default value Signup and view all the answers

Study Notes

SQL Data Definition and Data Types

SQL uses the terms table, row, and column to refer to relational database terms relation, tuple, and attribute.
The CREATE statement is the main SQL command for data definition.
The SQL Schema is identified by a schema name and includes descriptors for each element.
Schema elements include tables, constraints, views, domains, and other constructs.
SQL statements end with a semicolon.
The CREATE SCHEMA statement allows you to create a schema.
A catalog is a named collection of schemas in an SQL environment.
An SQL environment is the installation of an SQL-compliant RDBMS on a computer system.
Base tables are actually created and stored as a file by the DBMS.
Virtual relations are created through the CREATE VIEW statement.
Basic data types in SQL include numeric data types (integers, floats), character-string data types (fixed length, varying length), bit-string data types (fixed and varying length), boolean data types (TRUE, FALSE, NULL), DATE data types, TIMESTAMP data types, and INTERVAL data types.

Specifying Constraints in SQL

Constraints include key and referential integrity constraints, restrictions on attribute domains and NULLs, and constraints on individual tuples within a relation.
NOT NULL constraints ensure that NULL is not permitted for a particular attribute.
Default values can be set using the DEFAULT clause.
The CHECK clause can be used to set conditions for attributes.
The PRIMARY KEY clause specifies one or more attributes that make up the primary key of a relation.
The UNIQUE clause specifies alternate (secondary) keys.
The FOREIGN KEY clause specifies referential integrity constraints.
If there is an update violation, the default operation is to reject the update request.
Attach referential triggered action clauses to specify actions for violations.
The CASCADE option is suitable for "relationship" relations.
The CONSTRAINT keyword can be used to give names to constraints which is useful for altering them later.
CHECK clauses at the end of a CREATE TABLE statement can be used to specify constraints for each tuple individually.

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Description

This quiz covers the fundamentals of SQL data definition and various data types. Key topics include the CREATE statement, schema elements, and the differences between base tables and virtual relations. Test your knowledge on these essential SQL concepts.