SQL DEFAULT Constraint Example

The constraint DEFAULT defines a default value of a column.

  • The INSERT statement will insert a record with the default value when a value is explicitly not provided.

In the below example, the column country is defined using the DEFAULT keyword.

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CREATE TABLE customers (
    customer_id INT NOT NULL PRIMARY KEY,
    customer_name VARCHAR(30) NOT NULL,
    address VARCHAR(20),
    city VARCHAR(20),
    country VARCHAR(20) NOT NULL DEFAULT 'USA',
    postal_code VARCHAR(10)
);

In case the table already exists, it returns an error message, which can be avoided by including the keyword IF NOT EXISTS as shown below.

CREATE TABLE IF NOT EXISTS customers (
    customer_id INT NOT NULL PRIMARY KEY,
    customer_name VARCHAR(30) NOT NULL,
    address VARCHAR(20),
    city VARCHAR(20),
    country VARCHAR(20) NOT NULL DEFAULT 'USA',
    postal_code VARCHAR(10)
);

Overall

We now know when and how to use the DEFAULT constraint.

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