Thanks for your help,Rick. Followed your advice, I've solved the problem. Following is the solution:
select([table_name]).order_by(case([(table_name.c.s_date==None,table_name.c.f_date)],else_=table_name.c.s_date)) Thanks again :) On 11月9日, 上午1时48分, "Rick Morrison" <[EMAIL PROTECTED]> wrote: > Most database engines support a couple of SQL functions that help in cases > like this, read your database docs for either the ISNULL or the COALESCE > function. > > Another technique is to use an SQL CASE statement. > > For all three methods the idea is to supply a default value to substitute > when the value in question is NULL. > > In your case that substituted value would be the value of the 'f_date' > column, so in essence the logic would be "use the value of 's_date' > if it's NOT NULL, otherwise use the value of 'f_date'". > > SA has constructs for both the SQL function method and the CASE statemen > method; all are documented (well, I think the CASE is....) > > Rick > > On 11/8/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > > > > > > a table, say like this: > > name f_date s_dtae > > ------------------------------------------------ > > name1 2007-10-01 null > > name2 2007-06-03 2007-10-07 > > name3 2007-09-20 null > > name4 ... ... > > > the 'f_date' column always contains a value but the 's_date' can > > sometimes be null. > > now I want to get a collection -- all items will be in it and if the > > 's_date' is not null it must > > be ordered with 'f_date' of those the 's_date' is null. Just like > > this: > > > name f_date s_date > > ----------------------------------------------- > > name3 2007-09-20 null > > name1 2007-10-01 null > > name2 2007-06-03 2007-10-07 > > > any idea? use "select" query....maybe with 'UNION'? > > thanks in advance! > > > artman- 隐藏被引用文字 - > > - 显示引用的文字 - --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~----------~----~----~----~------~----~------~--~---
