How to Alter constraint in sql server?

Answer:

Alter Constraint:

Alter table <TableName> Add Constraint <constraintname>
Check(Columnname <100)
Go

Drop Constraint:

Alter Table <TableName> Drop Constraint <constraintname>
Go

Clean up

ALTER DATABASE <DataBaseName>
SET SINGLE_USER WITH ROLLBACK IMMEDIATE;
GO
DROP DATABASE <DataBasename>