DEFAULT constraint is used to set a default value to a column.
If you do not specify a value to insert a row, then can the default value (DEFAULT) having each column.
SQL DEFAULT in the CREATE TABLE
If you created an order, we do not specify the value of the column 'date', then for that column will be inserted by default to execute the function obtained GETDATE (), which returns the system date
Instead of a function, we can insert a specific value '2001-01-01 'or any other value.
SQL DEFAULT in the ALTER TABLE for MySQL
SQL DEFAULT in the ALTER TABLE statement to ORACLE, SQLSERVER, ACCESS:
To delete DEFAULT in MySQL
To delete DEFAULT in ORACLE, SQLSERVER, ACCESS: