Question

I asked almost the same question before, but I cannot use the MERGE syntax because of a sequencer. The problem is that we have price rules for people in a database. I want to synchronise these price rules for other people that should have the same rules.

+---------------------------+
| id | name | belongs_to_id |
|----+------+---------------+
| 1  | A    |               |
| 2  | B    | 1             |
| 3  | C    | 1             |
| 4  | D    |               |
+----+------+---------------+

Ok so now people B and C need, eventually, to have the same price rules as user A. So I have a pricerule table (simplified) like this:

+-----------------------------------+
| id | user_id | product_id | price |
+----+---------+------------+-------+
| 1  | 1       | 1          | 0.12  |
| 2  | 1       | 2          | 0.10  |
| 3  | 1       | 3          | 0.03  |
| 4  | 2       | 2          | 0.10  |
| 5  | 2       | 3          | 0.10  |
| 6  | 3       | 1          | 0.12  |
| 7  | 3       | 2          | 0.10  |
| 8  | 3       | 3          | 0.03  |
| 9  | 3       | 4          | 0.25  |
+----+---------+------------+-------+

So in this example, what should happen is:

• Give user 2 his price for product 1 with price 0.10
• Update price for user 2 product 3, to 0.03
• Delete price rule for user 3, product 4

I figured I have to take three steps: delete, update, add. I got the first two. But I’m thinking in circles about the insert statement. Basically I need to select all the price rules for user 1, then left join by product_id for each user. How do I do this for each user?

I am using Oracle 10.1

Answer 1

INSERT INTO
  priceRule
SELECT
  user.id,
  parentPriceRule.product_id,
  parentPriceRule.price
FROM
  user
LEFT JOIN
  priceRule    AS parentPriceRule
    ON  parentPriceRule.user_id = user.belongs_to_id
LEFT JOIN
  priceRule    AS myPriceRule
    ON  myPriceRule.user_id     = user.id
    AND myPriceRule.product_id  = parentPriceRule.product_id
WHERE
  myPriceRule.id IS NULL