← ACARA Digital Technologies Years 9–10

Entity

A type of thing a database stores data about, such as a student, book or order. Each entity becomes one table, and its name is a singular noun.

Part of: ACARA Digital Technologies Years 9–10 — Entities, Relationships and Queries — Module 7, QCE Digital Solutions Unit 2 — Data-Driven Problems and Solution Requirements — Module 51, QCE Digital Solutions Unit 2 — Data and Programming Techniques — Module 85, QCE Digital Solutions Unit 2 — Prototype Data Solutions — Module 3, QCE Digital Solutions Unit 3 — Interactions Between Users, Data and Digital Systems — Module 94, WA Computer Science ATAR Year 11 — Data Management — Module 22

Understanding Entity in ACARA Digital Technologies Years 9–10

What it does: The table is called book, not books, because each row stores one single book. Student and subject are two different types of thing, so they are two entities and each gets its own table. An entity is a type of thing we store data about, like a student. Happy is a feeling, not a thing with its own records. Each entity becomes one table. The details about it (name, year level) become the fields. Entities can be people, places, things or events. An order is an event worth storing data about. Entity and table names are singular nouns, so students should be student.

Common mistakes: Entity names are singular nouns. The table stores many students, but the entity is one type of thing, so it should be CREATE TABLE Student (. The closing bracket is missing. The entity table Loan should end with ) before the semicolon: CREATE TABLE Loan (id INT);.

Class: _____________________ · Name: _____________________ · Date: _________

Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

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This module's key terms are also in a printable crossword (Modules 433–451) and word search (Modules 413–451).

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Each concept is reinforced from every angle — learned, then applied, then tested.

Learning

Duo

Which of these is an entity a school database could store data about?

HappyStudent

Matches

CREATE TABLE students (studentId INT);

↓

The entity name is plural. It should be the singular noun student, because each row is one student.

Applying

Meanings

Term

entity

Meaning

A type of thing a database stores data about, such as a student, book or order. Each entity becomes one table, and its name is a singular noun.

Practice

SELECT studentId, firstName, yearLevel

Testing

Gaps

CREATE TABLE (bookId INT, title TEXT);

Check Answer

Spots

1-- Entity: student

2CREATE TABLE Students (

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Quick Questions

1. Which of these is an entity a school database could store data about?

A. Happy

B. Student ✓

An entity is a type of thing we store data about, like a student. Happy is a feeling, not a thing with its own records.

2. In a database design, each entity becomes...

A. One field

B. One table ✓

Each entity becomes one table. The details about it (name, year level) become the fields.

3. Which is the better name for an entity table that stores data about books?

A. Book ✓

B. Books and Stuff

Entity names are singular nouns that name one type of thing, so Book is a good choice.

4. A canteen database stores data about each order a student places. Is Order an entity?

A. Yes, an event can be an entity ✓

B. No, only people and objects can be entities

Entities can be people, places, things or events. An order is an event worth storing data about.

5. A library needs to record each person's name, phone number and email. Which of these is the entity?

A. Member ✓

B. PhoneNumber

Member is the type of thing we store data about. Phone number is an attribute of that entity, so it becomes a field.

Match the Pairs

CREATE TABLE student (studentId INT, firstName VARCHAR(30)); → The entity Student becomes one table, named with a singular noun

Entity: Event (e.g. a school sports carnival) → An entity can be an event, not just a person, place or thing

An entity name should be a singular noun because each row is one example of it → CREATE TABLE book (bookId INT, title VARCHAR(50));

Each entity becomes its own table, so students and subjects need two tables → CREATE TABLE student (studentId INT); CREATE TABLE subject (subjectId INT);

CREATE TABLE students (studentId INT); → The entity name is plural. It should be the singular noun student, because each row is one student.

CREATE TABLE studentName (studentId INT); → A student's name is an attribute, not an entity. It should be a column in the student table, not its own table.

Key Term

entity

A type of thing a database stores data about, such as a student, book or order. Each entity becomes one table, and its name is a singular noun.

Fill in the Blanks

1. CREATE TABLE Book (bookId INT, title TEXT);

Hint: Type the singular noun that names the entity this table stores. Look at the field names for a clue.

2. CREATE TABLE Place (placeId INT, city TEXT);

Hint: Type the two-word command that turns an entity into a table.

3. INSERT INTO Student VALUES (1, 'Ava');

Hint: Type the singular table name for the entity that a person called Ava belongs to at school.

4. SELECT firstName FROM Student;

Hint: Type the keyword that says which entity's table to read the data from.

5. CREATE TABLE Event (eventId INT, name TEXT);

Hint: Type the field that identifies each record, using the entity name followed by Id.

Spot the Error

Question 1

A -- Entity: student

B CREATE TABLE Students (

C studentId INT,

D firstName VARCHAR(30)

E );

Line B — Entity names are singular nouns. The table stores many students, but the entity is one type of thing, so it should be CREATE TABLE Student (

Question 2

A -- Library entities

B CREATE TABLE Book (id INT);

C CREATE TABLE Member (id INT);

D CREATE TABLE Loan (id INT;

Line D — The closing bracket is missing. The entity table Loan should end with ) before the semicolon: CREATE TABLE Loan (id INT);

Question 3

A -- Each entity is one table

B CREATE Teacher TABLE (

C teacherId INT,

D name VARCHAR(30)

E );

Line B — The keywords are in the wrong order. The Teacher entity becomes a table with CREATE TABLE Teacher (

Question 4

A -- Sport entities

B CREATE TABLE Player (id INT);

C CREATE TABLE Teams (id INT);

D CREATE TABLE Game (id INT);

Line C — Entity names are singular nouns. The entity is Team, not Teams, so it should be CREATE TABLE Team (id INT);

Question 5

A CREATE TABLE Pet (id INT);

B INSERT INTO Pet VALUES (1);

C INSERT INTO Pet VALUES (2);

D SELECT * FROM Pets;

Line D — The entity was made into a table called Pet, so the query must use that same name. It should be SELECT * FROM Pet;

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