Presto 查询没有得到正确的值

Question

Require your help please.

I have a table name wqmram and i want to calculate the min and max value for a column name s6 by month wise. Min value should not be zero as i want minimum value which is above zero.

I have written the below query:
SELECT min(s6) AS Mins6,
max(s6) AS Maxs6,
partition_0,
partition_1
FROM wqmram
WHERE cast(s6 AS decimal(30,2)) != 0.00
GROUP BY partition_0,partition_1
ORDER BY partition_0,partition_1;

partition_0 is year and patition_1 is month. I get the results as below which is wrong:

    Mins6   Maxs6   partition_0 partition_1
1   1017    996 2019    11
2   1002    994 2019    12
3   00.09   958 2020    01
4   00.01   997 2020    02
5   100 999 2020    03
6   100 999 2020    04
7   1   99  2020    05
8   1000    998 2020    06

If you see the above result then minimum values are coming greater than maximum values and that too they are wrong.

Can somebody please let me know what is the issue?

Answer 1

You need to cast the string values to numbers before you compute their min and max , otherwise, they are compared string-wise; typically, '996' is greater than '1017' , since the former starts with '9' , while the latter starts with '1' .

It might be simpler to convert in a subquery rather than repeating the cast() expression in the outer query:

select 
    partition_0,
    partition_1
    min(s6) as mins6,
    max(s6) as maxs6
from (
    select partition_0, partition_1, cast(s6 as decimal(30,2)) s6 
    from wqmram
) t
where s6 != 0.00
group by partition_0,partition_1
order by partition_0,partition_1;