Use `ALTER TABLE table_name ADD column_name data_type;`
Example: `ALTER TABLE employees ADD age INT;`
Add multiple columns: `ALTER TABLE table_name ADD column1 data_type, ADD column2 data_type;`
Example: `ALTER TABLE employees ADD salary DECIMAL(10,2), ADD department VARCHAR(50);`
Add a column with a default value: `ALTER TABLE table_name ADD column_name data_type DEFAULT value;`
Example: `ALTER TABLE employees ADD status VARCHAR(20) DEFAULT ‘active’;`
Add a column with `NOT NULL`: `ALTER TABLE table_name ADD column_name data_type NOT NULL;`
Example: `ALTER TABLE employees ADD email VARCHAR(100) NOT NULL;`
Add a column at a specific position if supported: `ALTER TABLE table_name ADD column_name data_type AFTER existing_column;`
Example: `ALTER TABLE employees ADD phone VARCHAR(20) AFTER email;`