EXEC sp_MSforeachtable '
    declare @tblname varchar(255);
    SET @tblname =  PARSENAME("?",1);

    if not exists (select column_name from INFORMATION_SCHEMA.columns
                   where table_name = @tblname and column_name = ''CreatedOn'')
    begin
        ALTER TABLE @tblname ADD CreatedOn datetime NOT NULL DEFAULT getdate();
    end
'

EXEC sp_MSforeachtable '
if not exists (select * from sys.columns
               where object_id = object_id(''?'')
               and name = ''CreatedOn'')
begin
    ALTER TABLE ? ADD CreatedOn datetime NOT NULL DEFAULT getdate();
end';

EXEC sp_MSforeachtable '
    declare @tblname varchar(255);
    SET @tblname =  PARSENAME("?",1);
    declare @sql nvarchar(1000);

    if not exists (select column_name from INFORMATION_SCHEMA.columns
                   where table_name = @tblname and column_name = ''CreatedOn'')
    begin
        set @sql = N''ALTER TABLE '' +  @tblname + N'' ADD CreatedOn datetime NOT NULL DEFAULT getdate();''
        exec sp_executesql @sql
    end
'

EXEC sp_MSforeachtable '
    declare @tblname varchar(255);
    SET @tblname =  PARSENAME("?",1);

    if not exists (select column_name from INFORMATION_SCHEMA.columns
                   where table_name = @tblname and column_name = ''CreatedOn'')
    begin
        ALTER TABLE [?] ADD CreatedOn datetime NOT NULL DEFAULT getdate();
    end
'

EXEC sp_MSforeachtable '
    if not exists (select column_name from INFORMATION_SCHEMA.columns
                   where table_name = ''?'' and column_name = ''CreatedOn'')
    begin
        ALTER TABLE [?] ADD CreatedOn datetime NOT NULL DEFAULT getdate();
    end
'