How do I create a unique constraint on a
alter table MyTable
add constraint UK_MyTable_MyUniqueKey unique nonclustered (MyCol)
insert into MyTable (MyCol) values ('ABC')
insert into MyTable (MyCol) values ('abc') --causes a violation of UNIQUE KEY constraint 'UK_MyTable_MyUnqiueKey'
This will change the column to be case sensitive. I don't think there's any change to your constraint...
ALTER TABLE mytable ALTER COLUMN mycolumn VARCHAR(10) COLLATE SQL_Latin1_General_CP1_CS_AS
Any selects or joins on this column will become case sensitive as a result of this operation.