How to use SQL CASE result to compare a column and get another case result

Question

I'm trying to compare my case result (desirecountry) with an existing column (so.country_name) to get another case result (Final_Country_Map_Name):

     SELECT subs."user email", subs."user join date", subs.location,
                iso.country_name as iso_country, iso.country_id as iso_country_id, 
                    users.country, users.event_type,
    -- 1.  
    CASE  WHEN subs.location = iso.country_name THEN iso.country_name
             ELSE users.country END AS **desirecountry**,
    -- 2.
    CASE  WHEN **desirecountry** = iso.country_name THEN **desirecountry**
            --ELSE Null END AS **Final_Country_Map_Name**
          
    FROM subs
    LEFT JOIN
    iso
    ON
    subs.location = iso.country_name
    LEFT JOIN
    users
    ON
    users.user_id = subs."user email"

When I'm using the second CASE conditions the logic is failing, it's not giving the expected output, it's giving me a null value in "final_country_map_name" column instead of "desirecountry" value = United States. Any small help would be helpful, Thank you. Ex: Column names are:->

location | iso_country  |   country     | desirecountry  | final_country_map_name   &&& Column o/p are: -> 
U.s,      null,          United States,   United States,       null,

Answer 1

Finally I found the answer:

SELECT 
`user email`,
`user join date`,
location,
iso_country,
iso_country_id,
users.country,
users.event_type,
desirecountry,

---

CASE 
    WHEN EXISTS (SELECT TOP 1 * FROM iso_country WHERE country_name = desirecountry) 
    THEN desirecountry
ELSE Null 
END AS Final_Country_Map_Name

---

FROM (SELECT 
    subs.`user email`,
        subs.`user join date`,
        subs.location,
        iso.country_name AS iso_country,
        iso.country_id AS iso_country_id,
        users.country,
        users.event_type,
        CASE
            WHEN subs.location = iso.country_name THEN iso.country_name
            ELSE users.country
        END AS desirecountry
FROM
    subs
LEFT JOIN iso ON subs.location = iso.country_name
LEFT JOIN users ON users.user_id = subs.`user email`)

Answer 2

Your code looks more like postgre, than MySQL

Also for your information, you should not use spaces in column names and leave the desired output to the gui, that save a lot of time

I used the inner SubSELECT to gather the data and put the second CASE in the outer SELECT

SELECT 
    `user email`,
    `user join date`,
    location,
    iso_country,
    iso_country_id,
    users.country,
    users.event_type,
    desirecountry,
    CASE
        WHEN desirecountry = iso_country THEN desirecountry
        ELSE NULL
    END AS Final_Country_Map_Name
FROM
    (SELECT 
        subs.`user email`,
            subs.`user join date`,
            subs.location,
            iso.country_name AS iso_country,
            iso.country_id AS iso_country_id,
            users.country,
            users.event_type,
            CASE
                WHEN subs.location = iso.country_name THEN iso.country_name
                ELSE users.country
            END AS desirecountry
    FROM
        subs
    LEFT JOIN iso ON subs.location = iso.country_name
    LEFT JOIN users ON users.user_id = subs.`user email`)