CREATE TABLE

The SQL CREATE TABLE Statement

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

Here's a basic example of how to use the CREATE TABLE statement:

CREATE TABLE TableName (
    Column1Name DataType1,
    Column2Name DataType2,
    ...
    CONSTRAINT ConstraintName CONSTRAINT_TYPE (ConstraintCondition),
    ...
);

      

Let's break down the components of the CREATE TABLE statement:

• TableName: Specifies the name of the table you want to create.
• Column1Name, Column2Name, etc.: Define the names of the columns in the table.
• DataType1, DataType2, etc.: Specify the data types for each column.
• CONSTRAINT ConstraintName CONSTRAINT_TYPE (ConstraintCondition): Define constraints for the table. Constraints are optional and enforce rules on the data in the table. ConstraintName is an optional identifier for the constraint. CONSTRAINT_TYPE can be PRIMARY KEY, FOREIGN KEY, UNIQUE, CHECK, etc., depending on the type of constraint. ConstraintCondition specifies the condition that the data must satisfy for the constraint to be valid.

Here's a concrete example:

    CREATE TABLE Employees (
        EmployeeID INT PRIMARY KEY,
        FirstName VARCHAR(50),
        LastName VARCHAR(50),
        Age INT CHECK (Age >= 18),
        DepartmentID INT,
        FOREIGN KEY (DepartmentID) REFERENCES Departments(DepartmentID)
    );
   

In this example:

• The table Employees has columns EmployeeID, FirstName, LastName, Age, and DepartmentID.
• EmployeeID is defined as the primary key.
• The Age column has a CHECK constraint to ensure that the age is equal to or greater than 18.
• DepartmentID is a foreign key referencing the DepartmentID column in the Departments table.

This CREATE TABLE statement creates a table named Employees with the specified columns and constraints.