Update table with ordered values - sql

Question

i need to update a table ordering by price and reassigning the ordered price.
The price and values are grouped by idcategory. Here is an example:
| ID | idcategory | price | value |
| 1 | 1 | 10 | 3 |
| 2 | 1 | 12 | 30 |
| 3 | 1 | 43 | 9 |
| 4 | 1 | 32 | 23 |
| 5 | 2 | 38 | 13 |
| 6 | 2 | 8 | 26 |
| 7 | 2 | 3 | 34 |
| 8 | 2 | 10 | 12 |
. .. .. .. .. .. .. ... ... .. .. .. ..
I need to reorder the table grouping by idcategory reassigning the ordered value to the ordered price like this:
| ID | idcategory | price | value |
| 1 | 1 | 10 | 3 |
| 2 | 1 | 12 | 9 |
| 3 | 1 | 32 | 23 |
| 4 | 1 | 43 | 30 |
| 5 | 2 | 3 | 12 |
| 6 | 2 | 8 | 13 |
| 7 | 2 | 10 | 26 |
| 8 | 2 | 38 | 34 |
.. .. .. .. .. .. .. .. .. ... ..
database is a postgres 9.2.
any idea will be appreciated.
Thanks you and Happy new Year !!!
this is the updated working solution based on GarethD suggestion:
WITH OrderedValues AS
( SELECT Value,
Price,
idcategory,
ROW_NUMBER() OVER(PARTITION BY idcategory ORDER BY Value) AS ValueNum,
ROW_NUMBER() OVER(PARTITION BY idcategory ORDER BY Price) AS PriceNum
FROM T
), OrderedIDs AS
( SELECT ID,
idcategory,
ROW_NUMBER() OVER(PARTITION BY idcategory ORDER BY ID) AS RowNum
FROM T
), NewValues AS
( SELECT i.ID,
v.Value,
p.Price
FROM OrderedIDs i
INNER JOIN OrderedValues v
ON i.RowNum = v.ValueNum
AND i.idcategory = v.idcategory
INNER JOIN OrderedValues p
ON i.RowNum = p.PriceNum
AND i.idcategory = p.idcategory
)
UPDATE T
SET Price = v.Price,
Value = v.Value
FROM NewValues v
WHERE v.ID = T.ID;
SELECT *
FROM T;

Answer 1

You first need to rank your both your IDs (OrderedIDs), and your Price/Value combination (OrderedValues). Then you can matched the corresponding ranks (NewValues), and update your table accordingly:
WITH OrderedValues AS
( SELECT Value,
Price,
idcategory,
ROW_NUMBER() OVER(PARTITION BY idcategory ORDER BY Value, Price) AS RowNum
FROM T
), OrderedIDs AS
( SELECT ID,
idcategory,
ROW_NUMBER() OVER(PARTITION BY idcategory ORDER BY ID) AS RowNum
FROM T
), NewValues AS
( SELECT i.ID,
v.Value,
v.Price
FROM OrderedIDs i
INNER JOIN OrderedValues v
ON i.RowNum = v.RowNum
AND i.idcategory = v.idcategory
)
UPDATE T
SET Price = v.Price,
Value = v.Value
FROM NewValues v
WHERE v.ID = T.ID;
Example on SQL Fiddle