>What I mean is that I am executing a SQL against the INFORMATION_SCHEMA.KEY_USAGE object. It extracts the constraint column name of the table I am passing in the WHERE clause. So, once the SQL is executed, how can I use that field? The field name in the SQL is Constraint_Name.

DECLARE @CONSTRAINT_NAME nvarchar(128)

SELECT @CONSTRAINT_NAME = CONSTRAINT_NAME
  FROM INFORMATION_SCHEMA.KEY_USAGE   
  WHERE ...

DECLARE @sql varchar(4000) 
SET @sql = 'ALTER TABLE DROP CONSTRAINT ' + @CONSTRAINT_NAME 
EXECUTE (@sql)