Oracle CASE语句和

Question

I'm having trouble return the correct information with my select statement

table:

name1  | name2  | amount
------ | ------ | --------
Fred   | Fred   | 10
Bob    | Fred   | 15
Sam    | Sam    | 100

Here is my query

SELECT 
        CASE WHEN name1 <> name2 THEN name2
        ELSE name1 END as name,
        SUM(amount) as amount
FROM table
GROUP BY???

What I would like to see as a result:

name  | amount
----- | ------
Fred  | 25
Sam   | 100

I've tried using a group by and receive errors saying this is not a GROUP BY expression. If I don't use a group by I receive the error not a single-group group function. Is this type of query possible?

Answer 1

The GROUP BY clause has to evaluate to the same thing as your select clause did. Do this:

SELECT 
    CASE WHEN name1 <> name2 THEN name2 ELSE name1 END as calc_name,
    SUM(amount) as amount
FROM table
GROUP BY CASE WHEN name1 <> name2 THEN name2 ELSE name1 END 

Also, name is a reserved keyword, so I modified that alias slightly.

Answer 2

Try as

SELECT ename,SUM(amount) amount FROM (
SELECT 
        CASE WHEN name1 <> name2 THEN name2
        ELSE name1 END as ename,
        amount
FROM table)
GROUP BY ename