I was unable to run the following SQL commands. First I thought that it might be because "max" is not defined but on the internet there SQL scripts with "max". I cannot understand what is wrong with the script. May be version of the SQL Server is wrong. I get an error:
SQL Error (137): Must declare the scalar variable "@sql"

Code:

DECLARE @sql nvarchar(MAX) = ''

SELECT @sql += 'ALTER TABLE ' + Quotename(tbl.name) + '  DROP CONSTRAINT ' + Quotename(cons.name) + ';'
 FROM SYS.DEFAULT_CONSTRAINTS cons
 JOIN SYS.COLUMNS col ON col.default_object_id = cons.object_id
 JOIN SYS.TABLES tbl ON tbl.object_id = col.object_id
 WHERE col.[name] IN ('id_card_number');

--PRINT @sql
EXEC Sp_executesql @sql