DEFAULT

In a Relational Data model every column must have a value. This value can allow NULLs. A DEFAULT defined assigns a value for a column when the value is not supplied. Once created they can be bound to a column or a user defined data type. They are effective only when they are bound to specific columns or User Defined data types.
Default value for state = 'TX'

Creating Default
defaults are created using the CREATE DEFAULT command. DEFAULT names follow rules for identifiers, however, they can be created only in the current database.
Syntax
CREATE DEFAULT as < constant expression >
Example
CREATE DEFAULT State_Default as "TX"

Binding a Default
Once DEFAULT has been defined it can be bound to one or several columns, to a user defined data type using SP_BINDEFAULT system stored procedure.
Syntax
SP_BINDEFALT <default>, <object>
Example
sp_bindefault state_default, "customer.state"

UnBinding a Default
When a DEFAULT is no longer needed it can be unbound from a column or user defined data type using SP_UNBINDDEFAULT system stored procedure.
Syntax
SP_UNBINDEFAULT <object>
Example
sp_unbindefault "customer.state"

Dropping a Default
We can drop the default object if you no longer need it.
Syntax
DROP DEFAULT < default name >
Example
drop default state_default