IB Computer Science Topic A.2.4 Data Definition Language Revision Notes (SL/HL)

IB Computer Science Topic A.2.4 Data Definition Language Revision Notes (SL/HL) | RevisionDojo

Definition

Data Definition Language (DDL)

A subset of SQL used to define and manage the structure of a database.

A DDL includes commands that create, modify, and delete database objects such as:
1. Tables
2. Indexes
3. Schemas

Common Mistake

Note

DDL is distinct from Data Manipulation Language (DML), which handles the manipulation of data within the database, such as inserting, updating, or deleting records.

Basic DDL Commands

CREATE: Defines new database objects.
ALTER: Modifies existing database objects.
DROP: Deletes database objects.
TRUNCATE: Removes all rows from a table but retains its structure for future use.

Example

A table can be created using DDL as follows:
- CREATE TABLE Students ( StudentID INT PRIMARY KEY, Name VARCHAR(50), Age INT, EnrollmentDate DATE),
This command creates a table named Students with four columns: StudentID, Name, Age, and EnrollmentDate.
The following command below adds a new column Email to the existing Students table.
- ALTER TABLE Students
- ADD Email VARCHAR(100);

Importance of DDL in a Data Model

Defines the Structure of the Database

DDL translates the conceptual data model (e.g., ER diagrams) into a physical schema that the database can understand and manage.

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Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

Duis aute irure dolor in reprehenderit

Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit.

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

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Definition

Data Definition Language (DDL)

A subset of SQL used to define and manage the structure of a database.

A DDL includes commands that create, modify, and delete database objects such as:
1. Tables
2. Indexes
3. Schemas

Common Mistake

Note

DDL is distinct from Data Manipulation Language (DML), which handles the manipulation of data within the database, such as inserting, updating, or deleting records.

Basic DDL Commands

CREATE: Defines new database objects.
ALTER: Modifies existing database objects.
DROP: Deletes database objects.
TRUNCATE: Removes all rows from a table but retains its structure for future use.

Example

A table can be created using DDL as follows:
- CREATE TABLE Students ( StudentID INT PRIMARY KEY, Name VARCHAR(50), Age INT, EnrollmentDate DATE),
This command creates a table named Students with four columns: StudentID, Name, Age, and EnrollmentDate.
The following command below adds a new column Email to the existing Students table.
- ALTER TABLE Students
- ADD Email VARCHAR(100);

Importance of DDL in a Data Model

Defines the Structure of the Database

DDL translates the conceptual data model (e.g., ER diagrams) into a physical schema that the database can understand and manage.

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

1. System fundamentals2 subtopics

2. Computer organization1 subtopic

3. Networks1 subtopic

4. Computational thinking, problem-solving and programming3 subtopics

5. Abstract data structures (HL)1 subtopic

6. Resource management (HL)1 subtopic

7. Control (HL)1 subtopic

A. Databases4 subtopics

B. Modelling and simulation4 subtopics

C. Web science6 subtopics

D. Object-oriented programming (OOP)4 subtopics

IB Computer Science A.2.4 Data Definition Language Notes

1. System fundamentals2 subtopics

2. Computer organization1 subtopic

3. Networks1 subtopic

4. Computational thinking, problem-solving and programming3 subtopics

5. Abstract data structures (HL)1 subtopic

6. Resource management (HL)1 subtopic

7. Control (HL)1 subtopic

A. Databases4 subtopics

B. Modelling and simulation4 subtopics

C. Web science6 subtopics

D. Object-oriented programming (OOP)4 subtopics

Basic DDL Commands

Importance of DDL in a Data Model

Defines the Structure of the Database

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

Basic DDL Commands

Importance of DDL in a Data Model

Defines the Structure of the Database

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account