对一个表中的行求和，然后将其移至另一表

Question

How can I sum rows from one table (based on selected critiria) and move the outcome to another table.

I have a table related to costs within project:

Table "costs":

id| CostName |ID_CostCategory| PlanValue|DoneValue
-------------------------------------------------------
1 | books    |1              |100       |120
2 | flowers  |1              |90        |90
3 | car      |2              |150       |130
4 | gas      |2              |50        |45

and I want to put the sum of "DoneValue" of each ID_CostCategory into table "CostCategories"

Table "CostCategories":

id|name |planned|done
------------------------
1 |other|190    |takes the sum from above table
2 |car  |200    |takes the sum from above table

Many thanks

Answer 1

INSERT INTO CostCategories(id,name,planned,done)
SELECT ID_CostCategory, CostName, SUM(PlanValue), SUM(DoneValue)
FROM costs GROUP BY ID_CostCategory, CostName

Answer 2

I would not store this, because as soon as anything changes in Costs then CostCategories will be out of date, instead I would create a view eg:

CREATE VIEW CostCategoriesSum
AS
SELECT  CostCategories.ID,
        CostCategories.Name,
        SUM(COALESCE(Costs.PlanValue, 0)) AS Planned,
        SUM(COALESCE(Costs.DoneValue, 0)) AS Done
FROM    CostCategories
        LEFT JOIN Costs
            ON Costs.ID_CostCategory = CostCategories.ID
GROUP BY CostCategories.ID, CostCategories.Name;

Now instead of referring to the table, you can refer to the view and the Planned and Done totals will always be up to date.