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SQL CREATE TABLE

The CREATE TABLE statement is used to create a new table in a database. It defines the table structure, including column names, data types, and constraints.

 

Key Features of SQL CREATE TABLE

  • Creates a new table with specified columns.
  • Defines column data types (e.g., INT, VARCHAR, DATE).
  • Supports constraints (PRIMARY KEY, NOT NULL, UNIQUE, FOREIGN KEY).

 

SQL CREATE TABLE Syntax

CREATE TABLE table_name (
    column1 datatype constraint,
    column2 datatype constraint,
    ...
);

 

Example: Creating a Table

CREATE TABLE Employees (
    ID INT PRIMARY KEY,
    Name VARCHAR(100) NOT NULL,
    Age INT,
    Salary DECIMAL(10,2),
    DepartmentID INT
);

This creates an Employees table with:

  • ID: Primary key (unique and required).
  • Name: String (max 100 characters), cannot be NULL.
  • Age: Integer.
  • Salary: Decimal with 10 digits and 2 decimal places.
  • DepartmentID: Integer.

 

Example: Creating a Table with Constraints

CREATE TABLE Departments (
    DeptID INT PRIMARY KEY,
    DeptName VARCHAR(50) UNIQUE NOT NULL
);
  • DeptID: Primary key.
  • DeptName: Unique, cannot be NULL.

 

Creating a Table with a Foreign Key

CREATE TABLE Employees (
    ID INT PRIMARY KEY,
    Name VARCHAR(100) NOT NULL,
    Age INT,
    Salary DECIMAL(10,2),
    DepartmentID INT,
    FOREIGN KEY (DepartmentID) REFERENCES Departments(DeptID)
);
  • DepartmentID references DeptID in the Departments table.

 

Checking Table Structure

To view table details:

DESCRIBE Employees;

or

SHOW COLUMNS FROM Employees;

 

Summary

  • CREATE TABLE defines a new table structure.
  • Use primary keys, foreign keys, and constraints for data integrity.
  • Use DESCRIBE or SHOW COLUMNS to check table structure.
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