SQL分区查询中的输出不正确

Question

I have a table with the initial values as:

+---------------------------------------+
| Entity  Country   Month_No.   Reports |
+---------------------------------------+
| FC        US         10          2    |
| FC        US         10          3    |
| FC        GER        10          4    |
| FC        GER        10          7    |
| FC        US         11          5    |
| FC        GER        11          8    |
+---------------------------------------+

I tried running a query on this table using this code:

SELECT entity, country, mnth, SUM(reports) OVER (PARTITION BY mnth) FROM practice1;

The output that I got from this code was:

+---------------------------------------+
| Entity  Country   Month_No.   Reports |
+---------------------------------------+
| FC        US         10          16   |
| FC        US         10          16   |
| FC        GER        10          16   |
| FC        GER        10          16   |
| FC        US         11          13   |
| FC        GER        11          13   |
+---------------------------------------+

The expected output should be like this:

+---------------------------------------+
| Entity  Country   Month_No.   Reports |
+---------------------------------------+
| FC        US         10          5    |
| FC        GER        10          11   |
| FC        US         11          5    |
| FC        GER        11          8    |
+---------------------------------------+

How do I get this as output?

Answer 1

Your problem can be solved with a simple group by :

SELECT entity, country, mnth, SUM(reports) 
FROM practice1
GROUP BY entity, country, mnth

Answer 2

You're summing reports by month, not by entity, country, and month. Adding entity and country to the partition by clause gets you the numbers you want, but now there are some duplicate rows because there are multiple rows with the same entity, country, and month. You can add distinct to get rid of those.

SELECT distinct entity, country, mnth, 
    SUM(reports) OVER (PARTITION BY entity, country, mnth)
FROM practice1;

Do you need to use partition by ? Seems like you're better off just using group by .

SELECT entity, country, mnth, SUM(reports)
FROM practice1;
GROUP BY entity, country, mnth