distance
area1
area2

distance = 3456
area1 = phoenix
area2 = houston

UPDATE dsl_checkins DC
    join area_distance AD
    on AD.area2 = DC.area
set DC.usage_flag=1,
    DC.id = (SELECT @dsl_id := DC.id)
WHERE DC.active = 1 AND
      DC.offline = 0 AND
      usage_flag = 0 AND
      AD.area1 = 'houston'
ORDER BY AD.distance ASC, RAND()
limit 1;

Error Code: 1221. Incorrect usage of UPDATE and ORDER BY

UPDATE Ratemaster
SET Ratemaster.Rate =
(
    SELECT Rates.Rate
    FROM Rates
    WHERE Ratemaster.user = Rates.user
    ORDER BY Rates.id
    LIMIT 1
)

(SELECT @dsl_id := DC.id)

SELECT * FROM dsl_checkins WHERE id = (SELECT @dsl_id) 

id   area1          area2            distance       
1    houston      phoenix         1235.345
2    dallas         phoenix         32432.453
3    newyourk   atlanta           32432.453
...

id   area        active        usage_flag ....       
1    houston      1                  0
3    houston      1                  0
4    houston      0                  1
5    dallas       0                  0
...
...

ORDER BY AD.distance ASC, RAND()
limit 1;