"#1054 - Unknown column" error when alias is used with-in the query?

While using 开发者_如何学Pythonthe following query, I get the error

#1054 - Unknown column 'plus' in 'field list'

when plus-minus is used. Otherwise, query runs fine. I guess there is something related to Aliases which I do not know how to use. Please guide!

Thanks.

Query:

SELECT users.name,
count(*) as total, 
SUM(sms.views)+ SUM(sms.downloads)+ (SELECT count(*) FROM `smsfb` WHERE (`feedback`=1 OR `feedback`=100) AND userid=users.uniqueID) AS plus,
SUM(sms.delreq)+(SELECT count(*) FROM `smsfb` WHERE (`feedback`=5 OR `feedback`=6) AND userid=users.uniqueID) AS minus,
plus-minus
FROM sms,users
WHERE sms.deviceID=users.uniqueID AND sms.catid!=23 AND sms.catid!=44 AND sms.catid!=45
AND date>="2011-10-03" AND date<"2011-10-09" 
GROUP BY users.uniqueID HAVING total>10 ORDER BY total DESC LIMIT 0, 10

---

You can't use the alias of a column inside the select part of the query.

You could do it in this way:

SELECT name
     , total
     , plus
     , minus
     , plus - minus
 FROM (
    SELECT users.name,
    count(*) as total, 
    SUM(sms.views)+ SUM(sms.downloads)+ (SELECT count(*) FROM `smsfb` WHERE     (`feedback`=1 OR     `feedback`=100) AND userid=users.uniqueID) AS plus,
    SUM(sms.delreq)+(SELECT count(*) FROM `smsfb` WHERE (`feedback`=5 OR `feedback`=6)     AND     userid=users.uniqueID) AS minus
    FROM sms,users
    WHERE sms.deviceID=users.uniqueID
      AND sms.catid!=23 AND sms.catid!=44
      AND sms.catid!=45
      AND date>="2011-10-03" AND date<"2011-10-09" 
    GROUP BY users.uniqueID HAVING total>10 ORDER BY total DESC
    LIMIT 0, 10
 ) plusAndMinus

From Problems with Column Aliases:

You can use the alias in GROUP BY, ORDER BY, or HAVING clauses to refer to the column