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_dates_dtae
name12007-10-01 null
name22007-06-03 2007-10-07
name32007-09-20 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_dates_date
---
name3 2007-09-20 null
name1 2007-10-01 null
name2 2007-06-03 2007-10-07
any idea? use select querymaybe with 'UNION'?
thanks in advance!
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