Re: Insert Data Into Tables Linked by Foreign Key

From: Alban Hertroys <dalroi(at)solfertje(dot)student(dot)utwente(dot)nl>
To: Yan Cheng Cheok <yccheok(at)yahoo(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Insert Data Into Tables Linked by Foreign Key
Date: 2010-01-04 11:57:31
Message-ID: 2EEDE41A-EE46-4176-BC91-9C65A03A863D@solfertje.student.utwente.nl
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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.

Alban Hertroys

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