Default Constraints in SQL Server

A Default Constraints enters a value in a column when one is not specified in an Insert statement. Default constraints enforces Domain integrity.

Consider the following facts before you implement a Default Constraints.

• A Default Constraints applies only to Insert Statement.
• Each column can have only one Default Constraint.
• Column with IDENTITY property or the Row Version data type can not have a default constraints placed on them.
• A Default Constraints allows some system supplied values or User. (CURRENT USER,SESSION_USER, SYSTEM_USER OR CURRENT _TIMESTAMP)

When to use  DEFAULT CONSTRAINTS?

• The data stored in a column has an obvious default value.
• The column does not accept null values.
• the column does not enforce unique values.