DECLARE @DF_NAME VARCHAR(200)
SELECT @DF_NAME =NAME FROM SYSOBJECTS WHERE XTYPE='D' AND PARENT_OBJ=OBJECT_ID('corporation')
AND EXISTS(SELECT * FROM SYSCOLUMNS WHERE ID=OBJECT_ID('corporation') AND INFO=COLID AND NAME='Enames')
EXEC ('ALTER TABLE corporation DROP CONSTRAINT '+@DF_NAME )