What is default value ? How do you define it ? What is the default value of column for which no default value is define ?

A default value is a predefined value assigned to a column in a database table. It can be specified using the DEFAULT clause when defining the table's schema. If no default value is defined for a column, and a new row is inserted into the table without providing a value for that column, the column's default value will be NULL, unless the column is defined with a NOT NULL constraint. In such cases, an error will occur if a value is not provided.