CREATE TABLE syntax in SQL

Introduction

We use CREATE TABLE to make a new table in a database where we can store information in rows and columns.

When starting a new project and you need to organize data like users or products.

When you want to add a new category of data to your existing database.

When you need to create a temporary table to hold data for a specific task.

When designing a database to keep track of things like books in a library.

When setting up a database for a small business to store customer orders.

Syntax

SQL

CREATE TABLE table_name (
  column1 datatype [constraints],
  column2 datatype [constraints],
  ...
);

Each column needs a name and a datatype like INTEGER or TEXT.

Constraints like PRIMARY KEY or NOT NULL help keep data correct.

Examples

Creates a table named Students with three columns: ID, Name, and Age.

SQL

CREATE TABLE Students (
  ID INTEGER PRIMARY KEY,
  Name TEXT NOT NULL,
  Age INTEGER
);

Creates a Products table with an ID, name, and price.

SQL

CREATE TABLE Products (
  ProductID INTEGER PRIMARY KEY,
  ProductName TEXT,
  Price REAL
);

Creates an Orders table with order ID and date.

SQL

CREATE TABLE Orders (
  OrderID INTEGER PRIMARY KEY,
  OrderDate TEXT NOT NULL
);

Sample Program

This query creates a table called Employees with four columns to store employee details.

SQL

CREATE TABLE Employees (
  EmployeeID INTEGER PRIMARY KEY,
  FirstName TEXT NOT NULL,
  LastName TEXT NOT NULL,
  Email TEXT
);

Important Notes

Table names should be unique in the database.

Datatypes define what kind of data each column can hold.

Use PRIMARY KEY to uniquely identify each row.

Summary

CREATE TABLE makes a new table to store data.

You define columns with names and datatypes inside parentheses.

Constraints help keep your data organized and accurate.

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