How to Use DEFAULT in SQL

The DEFAULT constraint is used to specify a default value for a column. This value is automatically assigned when no value is provided during an INSERT.

Syntax:

CREATE TABLE table_name (    column_name datatype DEFAULT default_value,    ...);

Or add a default to an existing column:

ALTER TABLE table_nameALTER COLUMN column_name SET DEFAULT default_value;

Example 1: Create Table with DEFAULT

CREATE TABLE employees (    employee_id INT PRIMARY KEY,    name VARCHAR(100),    status VARCHAR(20) DEFAULT 'active',  -- Default status is 'active'    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP  -- Default to current time);

Example 2: Insert Without Specifying Default Column

INSERT INTO employees (employee_id, name) VALUES (101, 'John Doe');-- 'status' will be 'active' automatically

Notes:

• The DEFAULT value can be a constant, expression, or function (like CURRENT_TIMESTAMP).

• If you explicitly insert NULL, the default is not applied unless the column is defined as DEFAULT with NOT NULL.

• Syntax to add/change default may vary between databases (e.g., in MySQL use ALTER TABLE ... ALTER COLUMN ... SET DEFAULT or MODIFY COLUMN).

If you want, I can show you how to add or modify a default value in your database!