CREATE TABLE syntax in SQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

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

The CREATE TABLE statement is used to make a new table in a database where data can be stored in rows and columns.

beginner

Which keyword is used to define a column's data type in a CREATE TABLE statement?

The data type of a column is defined right after the column name, for example: column_name INT means the column stores integers.

intermediate

What does the PRIMARY KEY constraint do in a CREATE TABLE statement?

PRIMARY KEY ensures that each row in the table has a unique and not null value in that column, helping to identify each record uniquely.

beginner

Write the basic syntax to create a table named 'Students' with columns 'ID' as integer and 'Name' as text.

CREATE TABLE Students (ID INT, Name TEXT);

intermediate

Can you add a NOT NULL constraint to a column in CREATE TABLE? What does it mean?

Yes, adding NOT NULL means the column must always have a value; it cannot be left empty when inserting data.

Which SQL command is used to create a new table?

A SELECT

B INSERT INTO

C DROP TABLE

D CREATE TABLE

CREATE TABLE is the command used to make a new table in the database.

In the statement CREATE TABLE People (Age INT);, what does INT specify?

A The data type of the column

B The column name

C The table name

D A constraint

INT specifies that the Age column will store integer numbers.

What does the PRIMARY KEY constraint ensure?

A Column values are optional

B Column values can be duplicated

C Column values must be unique and not null

D Column values are always text

PRIMARY KEY makes sure each value in the column is unique and not empty.

Which of these is a valid CREATE TABLE syntax?

A CREATE TABLE (Name TEXT, Age INT);

B CREATE TABLE Students (Name TEXT, Age INT);

C CREATE Students TABLE (Name TEXT, Age INT);

D CREATE TABLE Students Name TEXT, Age INT;

The correct syntax includes the table name followed by columns in parentheses.

What does NOT NULL mean when used in a column definition?

A The column must always have a value

B The column can have empty values

C The column is optional

D The column stores numbers only

NOT NULL means the column cannot be left empty when inserting data.

Explain the basic structure of a CREATE TABLE statement and what each part does.

Think about how you tell the database to make a new box with labeled sections.

Describe how constraints like PRIMARY KEY and NOT NULL affect the data stored in a table.

Constraints are rules that keep the data clean and organized.

Practice

1. What does the CREATE TABLE statement do in SQL?

easy

A. It deletes an existing table.

B. It selects data from a table.

C. It updates data inside a table.

D. It creates a new table in the database.

Solution

1. Step 1: Understand the purpose of CREATE TABLE

   The CREATE TABLE command is used to make a new table to store data in a database.

2. Step 2: Compare with other SQL commands

   Deleting, updating, or selecting data are done by other commands like DROP, UPDATE, and SELECT.

3. Final Answer:

   It creates a new table in the database. -> Option D

4. Quick Check:

   CREATE TABLE = create new table [OK]

Hint: Remember: CREATE TABLE makes new tables [OK]

Common Mistakes:

• Confusing CREATE with DROP or SELECT
• Thinking CREATE modifies data inside tables
• Mixing CREATE TABLE with UPDATE command

2. Which of the following is the correct syntax to create a table named Students with columns id (integer) and name (text)?

easy

A. CREATE TABLE Students (id INT, name TEXT);

B. CREATE Students TABLE (id INT, name TEXT);

C. CREATE TABLE Students id INT, name TEXT;

D. CREATE TABLE Students {id INT, name TEXT};

Solution

1. Step 1: Check the correct order of keywords

   The correct order is CREATE TABLE table_name (columns);. CREATE TABLE Students (id INT, name TEXT); follows this.

2. Step 2: Verify column definitions and punctuation

   Columns must be inside parentheses and separated by commas. CREATE TABLE Students (id INT, name TEXT); uses parentheses and commas correctly.

3. Final Answer:

   CREATE TABLE Students (id INT, name TEXT); -> Option A

4. Quick Check:

   CREATE TABLE + (columns) syntax = CREATE TABLE Students (id INT, name TEXT); [OK]

Hint: Use parentheses around columns after table name [OK]

Common Mistakes:

• Placing TABLE keyword after table name
• Missing parentheses around columns
• Using curly braces instead of parentheses

3. What will happen if you run this SQL statement?

CREATE TABLE Employees (emp_id INT PRIMARY KEY, emp_name VARCHAR(50));

medium

A. Creates a table Employees with emp_id as unique key and emp_name as text.

B. Creates a table Employees but emp_id is not unique.

C. Syntax error because VARCHAR is not allowed.

D. Creates a table Employees but emp_name cannot store text.

Solution

1. Step 1: Understand column definitions

   The statement defines emp_id as an integer and sets it as PRIMARY KEY, which means it must be unique.

2. Step 2: Check data types and constraints

   VARCHAR(50) is a valid type for text up to 50 characters. So emp_name can store text.

3. Final Answer:

   Creates a table Employees with emp_id as unique key and emp_name as text. -> Option A

4. Quick Check:

   PRIMARY KEY = unique key, VARCHAR = text [OK]

Hint: PRIMARY KEY means unique; VARCHAR stores text [OK]

Common Mistakes:

• Thinking VARCHAR is invalid
• Assuming PRIMARY KEY allows duplicates
• Confusing data types with constraints

4. Identify the error in this SQL statement:

CREATE TABLE Orders order_id INT, order_date DATE;

medium

A. Incorrect data type for order_date.

B. Missing parentheses around column definitions.

C. Table name cannot be Orders.

D. Missing semicolon at the end.

Solution

1. Step 1: Check syntax for column definitions

   Column names and types must be inside parentheses after the table name.

2. Step 2: Verify other parts

   Data types and table name are valid, and semicolon is present.

3. Final Answer:

   Missing parentheses around column definitions. -> Option B

4. Quick Check:

   Columns must be inside ( ) [OK]

Hint: Always use parentheses around columns in CREATE TABLE [OK]

Common Mistakes:

• Omitting parentheses around columns
• Using wrong data types without error
• Confusing table name rules

5. You want to create a table Products with columns product_id (integer, unique), product_name (text), and price (decimal). Which SQL statement correctly enforces uniqueness on product_id using PRIMARY KEY?

hard

A. CREATE TABLE Products (product_id INT UNIQUE, product_name TEXT, price DECIMAL);

B. CREATE TABLE Products (product_id INT, product_name TEXT, price DECIMAL UNIQUE);

C. CREATE TABLE Products (product_id INT PRIMARY KEY, product_name TEXT, price DECIMAL);

D. CREATE TABLE Products (product_id INT, product_name TEXT UNIQUE, price DECIMAL);

Solution

1. Step 1: Understand uniqueness constraints

   Both UNIQUE and PRIMARY KEY enforce uniqueness, but PRIMARY KEY also disallows NULLs and is preferred for IDs.

2. Step 2: Analyze options for correct uniqueness on product_id

   CREATE TABLE Products (product_id INT UNIQUE, product_name TEXT, price DECIMAL); uses UNIQUE on product_id, which works but PRIMARY KEY is better. CREATE TABLE Products (product_id INT PRIMARY KEY, product_name TEXT, price DECIMAL); uses PRIMARY KEY on product_id, which is the best practice.

3. Final Answer:

   CREATE TABLE Products (product_id INT PRIMARY KEY, product_name TEXT, price DECIMAL); -> Option C

4. Quick Check:

   PRIMARY KEY = unique + not null [OK]

Hint: Use PRIMARY KEY for unique IDs [OK]

Common Mistakes:

• Putting UNIQUE on wrong column
• Confusing UNIQUE with PRIMARY KEY
• Not enforcing uniqueness on ID column