Databases - T03 SQL DDL Quiz

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Questions and Answers

Which of the following data types can store variable-length character strings with a maximum length specified in bytes?

VARCHAR2 (correct)

DATE

FLOAT

NUMBER

What is the purpose of the `CREATE TABLE` statement in SQL?

To define the schema of a new table in a database (correct)

To delete existing data from a table

To modify the structure of an existing table

To insert data into an existing table

What is the maximum length of a VARCHAR2 data type in Oracle?

1024 bytes

4000 bytes

255 characters

The maximum length is determined by the database administrator and can vary (correct)

What data type would you use to store a person's name in a database?

VARCHAR2 (D) Signup and view all the answers

What does the `scale` parameter in the `NUMBER` data type represent?

The number of digits after the decimal point (C) Signup and view all the answers

Which of the following data types is a subtype of the `NUMBER` data type?

FLOAT (C) Signup and view all the answers

What is the valid date range for the `DATE` data type in Oracle?

January 1, 4712 BC to December 31, 9999 AD (C) Signup and view all the answers

What does the fractional_seconds_precision in a TIMESTAMP specify?

The number of digits in the fractional part of the second (D) Signup and view all the answers

At which level can a constraint refer to only one column?

Column level (C) Signup and view all the answers

Which SQL command is used to create foreign key constraints?

ALTER TABLE (D) Signup and view all the answers

What does the CHECK constraint in the RaceType table enforce?

Distance must be between 50 and 1500 (D) Signup and view all the answers

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

To create a unique identifier for table records (D) Signup and view all the answers

In which table is the Gender constraint enforced?

Coach (B) Signup and view all the answers

Which component is necessary when defining a foreign key constraint?

A referenced table with a primary key (C) Signup and view all the answers

In the Coaching table, what type of relationships can be enforced between SwimmerCode and Swimmer?

One-to-many (C) Signup and view all the answers

What data type is used for the StyleID in the Style table?

number(4) (A) Signup and view all the answers

What is an identity column in SQL?

A column that automatically generates a unique number (B) Signup and view all the answers

In the RaceResult table, which column is not required to be unique?

Cassification (A) Signup and view all the answers

What does the ADD CONSTRAINT command do in SQL?

Adds a new constraint to an existing table (B) Signup and view all the answers

What is enforced by the NOT NULL constraint in a column?

The column cannot store NULL values (D) Signup and view all the answers

What does the command 'GENERATED AS IDENTITY' imply in a table definition?

The column's value will be auto-incremented (C) Signup and view all the answers

Study Notes

Databases - T03 SQL Data Definition Language Subset (DDL)

SQL is more than just a query language; it's used to define data structures, change data, and specify security.
SQL's DDL subset is used for defining the structure of a database.
DDL statements include CREATE TABLE, CREATE INDEX, CREATE VIEW, DROP TABLE, TRUNCATE TABLE, and ALTER TABLE statements, which are used to create new database objects such as tables, indexes, views, delete and empty tables, and alter database objects
CREATE TABLE is used to build new tables, defining column names and data types (e.g., VARCHAR2, NUMBER, DATE).
DROP TABLE is used to remove a table and all its data.
Different data types (e.g., VARCHAR2, NVARCHAR2, NUMBER, FLOAT, DATE, TIMESTAMP) exist in SQL databases, each storing different kinds of data. Understanding these data types is essential for designing effective schemas.

SQL-Structured Query Language

SQL encompasses defining data structure, modifying database contents, and security.
Different categories (DDL, DML, DCL) exist within SQL, defining distinct functions.
DDL (Data Definition Language): creating, changing, and removing database objects (tables, views, indices, etc.)
DML (Data Manipulation Language): working with data in tables (inserting, deleting, selecting, etc. data)
DCL (Data Control Language): managing access permissions to database objects using statements like GRANT, REVOKE, ADD, and DELETE.

CREATE TABLE Statement

Used to build new tables in the database.
Column parameters specify the names of the columns within each table.
Data types (e.g., VARCHAR, INTEGER, DATE) determine the kind of data a column can hold.
The CREATE TABLE statement defines a new table with the specified columns.
Example: CREATE TABLE table_name (column1 datatype, column2 datatype, ...);
DROP TABLE statement deletes an existing table and all its data.

Some Oracle Data Types

VARCHAR2(size): A variable-length character string.
NVARCHAR2(size): A variable-length Unicode character string.
NUMBER [(p [, s])]: A numeric data type with precision (p) and scale (s).
FLOAT [(p)]: A floating-point number with precision (p).
DATE: Stores dates and times.
TIMESTAMP [(fractional_seconds_precision)]: Stores timestamps with fractional seconds.

CREATE TABLE Constraints

Integrity constraints help ensure data consistency (e.g., primary key, foreign key).
Value constraints define rules for column values (e.g., NOT NULL, unique values, specific value ranges - CHECK constraint).
Constraints can be added to an existing table or defined at table creation.
Constraints are classified as column-level or table-level.
Column-level constraints apply to an individual column.
Table-level constraints apply to more than one column.

DDL Example (GoldFish Problem)

A possible database schema for a "GoldFish" problem is presented visually with relationships between tables
This illustrated schema represents a possible database design for the "GoldFish" problem.

CREATE TABLE Example

Example CREATE TABLE statements for RaceType, Style, Coach, Coaching, Swimmer, and RaceResult tables showcasing the use of constraints and data types

RaceType and Style Table Example Constraints

RaceType and Style table examples showcase value constraints, including a CHECK constraint for Distance and primary key
Example usage of ALTER TABLE and FOREIGN KEY for relationships between tables

Coach and Coaching Table Example Constraints

Example Coach and Coaching table examples demonstrate value constraints and PRIMARY KEY and FOREIGN KEY constraints.

Race Table Integrity Constraints

Example Race table constraint definition including constraints.

Swimmer and RaceResult Table Integrity Constraints

Example Swimmer and RaceResult tables demonstrating the use of integrity constraints, data types, and primary keys.

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Description

This quiz tests your understanding of SQL Data Definition Language (DDL) and its subset functionalities. Topics include defining database structures, DDL statements like CREATE and DROP TABLE, and various data types. Prepare to enhance your skills in database design and management.