← VCE Data Analytics U3O1

SQL column data types and sizes

A column's data type and size set in CREATE TABLE. VARCHAR(50) holds text up to 50 characters. Other types: INT, DECIMAL(8,2), DATE, BOOLEAN. They control what a column stores.

Part of: VCE Data Analytics - U3O1 - Data Analytics — Module 18, ACARA Digital Technologies Years 9–10 — Entities, Relationships and Queries — Module 22, QCE Digital Solutions Unit 2 — Data and Programming Techniques — Module 35, QCE Digital Solutions Unit 2 — Prototype Data Solutions — Module 6, QCE Digital Solutions Unit 3 — Innovative Digital Solutions — Module 20, WA Computer Science ATAR Year 11 — Data Management — Module 50

Understanding SQL column data types and sizes in VCE Data Analytics U3O1

What it does: INT holds whole numbers with no decimal part, so it suits counts, ages and scores. The DATE type is used for calendar dates, so the database can sort and compare them correctly. VARCHAR(n) stores text up to n characters. INT only stores whole numbers, so it cannot hold names. In DECIMAL(p,s), p is the total number of digits and s is the number of digits after the decimal point. It is ideal for prices like 4.50. INT would drop the cents. DECIMAL(8,2) keeps two decimal places. VARCHAR needs a size in brackets, such as VARCHAR(10), so the database knows the maximum number of characters.

Common mistakes: VARCHAR must have a size in brackets to say the maximum number of characters. It should be VARCHAR(50). DECIMAL takes two numbers separated by a comma: precision and scale. It should be DECIMAL(6,2), not DECIMAL(6.2).

Class: _____________________ · Name: _____________________ · Date: _________

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This module's key terms are also in a printable crossword (Modules 17–49) and word search (Modules 17–91).

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Learning

Duo

Which column type is best for a student's first name?

firstName VARCHAR(50)firstName INT

Matches

lastName VARCHAR

↓

VARCHAR has no size. A maximum number of characters is needed, for example VARCHAR(50).

Applying

Meanings

Term

VARCHAR(50)

Meaning

A column's data type and size set in CREATE TABLE. VARCHAR(50) holds text up to 50 characters. Other types: INT, DECIMAL(8,2), DATE, BOOLEAN. They control what a column stores.

Practice

CREATE TABLE club (

Testing

Gaps

firstName (50)

Check Answer

Spots

1CREATE TABLE Student (

2 firstName VARCHAR,

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Quick Questions

1. Which column type is best for a student's first name?

A. firstName INT

B. firstName VARCHAR(50) ✓

VARCHAR(n) stores text up to n characters. INT only stores whole numbers, so it cannot hold names.

2. Which column type is best for a whole-number count such as stock?

A. stock INT ✓

B. stock DATE

INT stores whole numbers like 200 or 80. DATE is only for calendar dates.

3. What does the (8,2) mean in DECIMAL(8,2)?

A. 8 characters of text, and 2 rows allowed

B. Up to 8 digits in total, with 2 after the decimal point ✓

In DECIMAL(p,s), p is the total number of digits and s is the number of digits after the decimal point. It is ideal for prices like 4.50.

4. Which is the correct way to declare a price column that stores values like 12.50?

A. price DECIMAL(8,2) ✓

B. price INT

INT would drop the cents. DECIMAL(8,2) keeps two decimal places.

5. Which column is declared with a sensible type for an order date?

A. orderDate DATE ✓

B. orderDate BOOLEAN

DATE stores calendar dates such as 2026-02-03. BOOLEAN only stores true or false.

Match the Pairs

firstName VARCHAR(50) → A text column that can hold up to 50 characters

price DECIMAL(8,2) → A number column with up to 8 digits in total, 2 of them after the decimal point

A column that stores whole numbers only, such as a student's age or points → points INT

A column that stores a calendar date such as a birth date or order date → orderDate DATE

lastName VARCHAR → VARCHAR has no size. A maximum number of characters is needed, for example VARCHAR(50).

inStock INT → INT stores whole numbers, so it is the wrong type for a true/false value. BOOLEAN should be used.

Key Term

VARCHAR(50)

A column's data type and size set in CREATE TABLE. VARCHAR(50) holds text up to 50 characters. Other types: INT, DECIMAL(8,2), DATE, BOOLEAN. They control what a column stores.

Fill in the Blanks

1. CREATE TABLE students ( firstName VARCHAR(50) );

Hint: Type the data type used for text of varying length.

2. CREATE TABLE products ( stock INT );

Hint: Type the data type for whole numbers.

3. CREATE TABLE products ( price DECIMAL(8,2) );

Hint: Type the number of digits kept after the decimal point (the scale).

4. CREATE TABLE orders ( orderDate DATE );

Hint: Type the data type for calendar dates.

5. CREATE TABLE students ( isPrefect BOOLEAN );

Hint: Type the data type for a true or false value.

Spot the Error

Question 1

A CREATE TABLE Student (

B firstName VARCHAR,

C yearLevel INT,

D house VARCHAR(10)

E );

Line B — VARCHAR must have a size in brackets to say the maximum number of characters. It should be VARCHAR(50).

Question 2

A CREATE TABLE Product (

B productId INT,

C name VARCHAR(40),

D price DECIMAL(6.2),

E stock INT

F );

Line D — DECIMAL takes two numbers separated by a comma: precision and scale. It should be DECIMAL(6,2), not DECIMAL(6.2).

Question 3

A CREATE Orders TABLE (

B orderId INT,

C orderDate DATE

D );

Line A — The SQL keywords are in the wrong order. It should be CREATE TABLE Orders ( with the table name after TABLE.

Question 4

A CREATE TABLE Event

B eventName VARCHAR(30),

C eventDate DATE,

D isPublic BOOLEAN

E );

Line A — The column definitions must start inside an opening bracket. The line should end with ( so it reads CREATE TABLE Event (

Question 5

A CREATE TABLE Staff (

B staffId INT,

C hireDate DATE(10),

D salary DECIMAL(8,2)

E );

Line C — The DATE type has a fixed format and does not take a size. It should be just DATE.

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