Data extraction issue: Query does not return the expected result.

[hotsun1508]

Hi, I'm expecting different results when executing the query below.
There seems to be an issue with data extraction.
(I've checked that there's no problem with CASE WHEN usage: https://github.com/AlaSQL/alasql/wiki/CASE)

• AlaSQL query

SELECT 
    CASE 
        WHEN [age] BETWEEN 0 AND 9 THEN '0-9'
        WHEN [age] BETWEEN 10 AND 19 THEN '10-19'
        WHEN [age] BETWEEN 20 AND 29 THEN '20-29'
        WHEN [age] BETWEEN 30 AND 39 THEN '30-39'
        WHEN [age] BETWEEN 40 AND 49 THEN '40-49'
        WHEN [age] BETWEEN 50 AND 59 THEN '50-59'
        WHEN [age] BETWEEN 60 AND 69 THEN '60-69'
        WHEN [age] BETWEEN 70 AND 79 THEN '70-79'
        WHEN [age] BETWEEN 80 AND 89 THEN '80-89'
        WHEN [age] BETWEEN 90 AND 99 THEN '90-99'
        ELSE '100+'
    END AS [age_group],
    COUNT(*) AS [customer_count]
FROM 
    [temptable]
WHERE 
    [age] IS NOT NULL
GROUP BY 
    [age_group]
ORDER BY 
    [age_group];

• Result

0: {age_group: '100+', customer_count: 56046}

The data type of the age column is numeric, and the expected result when extracting this data is as follows.

agegroup	customer_count
20-29	6928
30-39	19188
40-49	16326
50-59	9272
60-69	3755
70-79	495
80-89	61
90-99	21

FYI, I've got this result by executing the same query in PostgreSQL.

SELECT 
    CASE 
        WHEN age BETWEEN 0 AND 9 THEN '0-9'
        WHEN age BETWEEN 10 AND 19 THEN '10-19'
        WHEN age BETWEEN 20 AND 29 THEN '20-29'
        WHEN age BETWEEN 30 AND 39 THEN '30-39'
        WHEN age BETWEEN 40 AND 49 THEN '40-49'
        WHEN age BETWEEN 50 AND 59 THEN '50-59'
        WHEN age BETWEEN 60 AND 69 THEN '60-69'
        WHEN age BETWEEN 70 AND 79 THEN '70-79'
        WHEN age BETWEEN 80 AND 89 THEN '80-89'
        WHEN age BETWEEN 90 AND 99 THEN '90-99'
        ELSE '100+'
    END AS agegroup,
    COUNT(*) AS customer_count
FROM 
    adventureworks."adventureworks-total"
WHERE 
   age IS NOT NULL
GROUP BY 
   agegroup
ORDER BY 
   agegroup;

The query isn't returning the expected results when I run it.
Could you help me out?
Thank you so much! 😊

[mathiasrw]

Very interesting.

 SELECT 
        CASE 
            WHEN age BETWEEN 0 AND 9 THEN '0-9'
            WHEN age BETWEEN 10 AND 19 THEN '10-19'
            WHEN age BETWEEN 20 AND 29 THEN '20-29'
            ELSE '30+'
        END AS age_group 
        
    FROM ? 
    --GROUP BY age_group 

Gives the expected result (see https://jsfiddle.net/bpkesrh2/ ) and if I want to group across the case column it returns "30+" (see https://jsfiddle.net/1jLnxdmz/1/ ) like you have uncovered.

BUT!!!

If I remove any values over 30 (see https://jsfiddle.net/1jLnxdmz/2/ ) it STILL returns 30+ when adding the group by back in (see https://jsfiddle.net/1jLnxdmz/3/ )

This indicate that the group by logic somehow fetches the value in theELSE clause - no matter the content actually selected.