close;
Connection := zs_dm.adocon_zssys;
SQL.Clear;
sql.Add('if not exists(select * from syscolumns where id=object_id(''table1'') and name in (''fld12'',''aa''))');
SQL.Add('begin');
SQL.Add(' alter table table1 add [fld12] varchar(200), [ParentNo] varchar(200),[Type] varchar(10)');
SQL.Add(' alter table table1 alter column [aa] text');
SQL.Add('end');