Re: Insert Data Into Tables Linked by Foreign Key

On 5 Jan 2010, at 4:26, Yan Cheng Cheok wrote:

> Can you please provide me an example of a stored procedures to achieve that?
>
> Thanks and Regards
> Yan Cheng CHEOK

Sure. The one below should even protect you against concurrent inserts. I didn't test it though, there may be some typos etc.

CREATE OR REPLACE FUNCTION insert_order(_customer_name, _price)
RETURNS integer
LANGUAGE 'plpgsql' STABLE
AS $body$
DECLARE
_customer_id int;
BEGIN
LOOP;
SELECT INTO _customer_id Customer_ID FROM Customer WHERE name = _customer_name;

EXIT WHEN FOUND;

BEGIN;
INSERT INTO Customer (name)
VALUES (_customer_name)
RETURNING Customer_ID INTO _customer_id;

EXIT;
EXCEPTION WHEN unique_violation THEN
-- Do nothing
END;
END LOOP;

INSERT INTO Order (Customer_ID, Price) VALUES (_customer_id, _price);
END;
$body$;

> --- On Mon, 1/4/10, Alban Hertroys <dalroi(at)solfertje(dot)student(dot)utwente(dot)nl> wrote:
>
>> From: Alban Hertroys <dalroi(at)solfertje(dot)student(dot)utwente(dot)nl>
>> Subject: Re: [GENERAL] Insert Data Into Tables Linked by Foreign Key
>> To: "Yan Cheng Cheok" <yccheok(at)yahoo(dot)com>
>> Cc: pgsql-general(at)postgresql(dot)org
>> Date: Monday, January 4, 2010, 7:57 PM
>> 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
>>
>> --
>> Screwing up is the best way to attach something to the
>> ceiling.
>>
>>
>>
>>
>>
>>
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>
>
>
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Alban Hertroys

--
Screwing up is the best way to attach something to the ceiling.

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