DECLARE @nameTable as nvarchar(512)
DECLARE @partSet as nvarchar(128)
DECLARE @partSetAndSep as nvarchar(128)
DECLARE @sqlDynamic as nvarchar(max)
DECLARE @partWhere as nvarchar(512)

SET @nameTable = 'mytab'
SET @partWhere = 'mark=0' 
SET @partSet = '=0 '
SET @partSetAndSep = @partSet + ', '

SELECT @sqlDynamic = 'UPDATE ' + QUOTENAME(@nameTable) + ' SET ' + STRING_AGG(QUOTENAME(cols.name), @partSetAndSep) + @partSet + ' WHERE ' + @partWhere +';' FROM sys.all_columns as cols INNER JOIN sys.all_objects as objs ON cols.object_id = objs.object_id WHERE objs.type ='U' AND objs.name = @nameTable

PRINT @sqlDynamic