CREATE TABLE

(show you how to create new tables in a database using the CREATE TABLE statement.)

Summary: in this tutorial, you will learn how to use the MySQL CREATE TABLE statement to create a new table in the database.

The CREATE TABLE statement is used to create a new table in a database. The syntax is thus:

CREATE TABLE table_name (
    column1 datatype,
    column2 datatype,
    column3 datatype,
   ....
);

The column parameters specify the names of the columns of the table.

The datatype parameter specifies the type of data the column can hold (e.g. varchar, integer, date, etc.).

Tip: For an overview of the available data types, go to our complete Data Types Reference.

MySQL CREATE TABLE Example

The following example creates a table called "Persons" that contains five columns: PersonID, LastName, FirstName, Address, and City:

CREATE TABLE Persons (
    PersonID int,
    LastName varchar(255),
    FirstName varchar(255),
    Address varchar(255),
    City varchar(255)
);

• The PersonID column is of type int and will hold an integer.
• The LastName, FirstName, Address, and City columns are of type varchar and will hold characters, and the maximum length for these fields is 255 characters.

The empty "Persons" table will now look like this:

Create Table Using Another Table

A copy of an existing table can also be created using CREATE TABLE.

The new table gets the same column definitions. All columns or specific columns can be selected.

If you create a new table using an existing table, the new table will be filled with the existing values from the old table.

Syntax

CREATE TABLE new_table_name AS
    SELECT column1, column2,...
    FROM existing_table_name
    WHERE ....;

The following SQL creates a new table called "TestTables" (which is a copy of the "Customers" table):

CREATE TABLE TestTable AS
SELECT customername, contactname
FROM customers;

Create a Table with Constraints

SQL constraints are used to specify rules for data in a table. Constraints can be specified when the table is created with the CREATE TABLE statement, or after the table is created with the ALTER TABLEstatement.

CREATE TABLE table_name (
    column1 datatype constraint,
    column2 datatype constraint,
    column3 datatype constraint,
    ....
);

Constraints are used to limit the type of data that can go into a table. This ensures the accuracy and reliability of the data in the table. If there is any violation between the constraint and the data action, the action is aborted.

Constraints can be column level or table level. Column level constraints apply to a column, and table level constraints apply to the whole table.

The following constraints are commonly used in SQL:

• NOT NULL - Ensures that a column cannot have a NULL value
• UNIQUE - Ensures that all values in a column are different
• PRIMARY KEY - A combination of a NOT NULL and UNIQUE. Uniquely identifies each row in a table
• FOREIGN KEY - Prevents actions that would destroy links between tables
• CHECK - Ensures that the values in a column satisfies a specific condition
• DEFAULT - Sets a default value for a column if no value is specified
• CREATE INDEX - Used to create and retrieve data from the database very quickly