In response to Alban Hertroys :
> On 4 Jan 2010, at 9:53, Yan Cheng Cheok wrote:
>
> > For example, "John" place "1.34" priced order.
> >
> > (1) Get Customer_ID from Customer table, where name is "John"
> > (2) If there are no Customer_ID returned (There is no John), insert "John"
> > (3) Get Customer_ID from Customer table, where name is "John"
> > (4) Insert "Customer_ID" and "1.34" into Order table.
> >
> > There are 4 SQL communication with database involved for this simple operation!!!
> >
> > Is there any better way, which can be achievable using 1 SQL statement?
>
>
> You don't need the 3rd statement if you use INSERT .. RETURNING at step 2.
>
> The one way you could achieve this by calling only one statement that
> I can think of is to wrap this in a stored procedure. Plain SQL
> doesn't provide any means to do what you want.
Writeable CTE can do that ;-)
http://wiki.postgresql.org/images/c/c0/PGDay2009-EN-Writeable_CTEs_The_Next_Big_Thing.pdf
Andreas
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Andreas Kretschmer
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