SQL Server cursor example

DECLARE db_cursor CURSOR FOR
SELECT name
FROM table
WHERE --some condition--

OPEN db_cursor 
FETCH NEXT FROM db_cursor INTO @name 

WHILE @@FETCH_STATUS = 0 
BEGIN 

--sql query using @name goes here--
FETCH NEXT FROM db_cursor INTO @name 
END 

CLOSE db_cursor 
DEALLOCATE db_cursor

SQL server query to drop default constraint and a column

declare @default sysname, @sql nvarchar(max)

select @default = name
from sys.default_constraints
where parent_object_id = object_id('MYTABLENAME')
AND type = 'D'
AND parent_column_id = (
select column_id
from sys.columns
where object_id = object_id('MYTABLENAME')
and name = 'MYCOLUMNNAME'
)

set @sql = N'alter table MYTABLENAME drop constraint ' + @default
exec sp_executesql @sql

alter table MYTABLENAME drop MYCOLUMNNAME

go