Cant display string value suddenly?

Grafana Configuration
1

Hi! I have been running grafana for almost a year with great success and with basically the same settings. But now suddenly no dashboards work any more?? I get the error:

Value column must have numeric datatype, column: value type: string value: 60.69

Im running a mysql server and have a online grafana setup. The colume is a varchar type in the sql database (and it have worked with time series for a year? but now i does not?)

the query follows this pattern ;

SELECT
UNIX_TIMESTAMP(timestamp) as time_sec,
data as value,
topic as metric
FROM mqtt
WHERE $__timeFilter(timestamp) and ‘temperatur/innetemp’ in(topic)
ORDER BY timestamp ASC

grafana online service is version v5.2.3 (commit: cf4c090)

Any pointers? Thanks

2

I will answer my own question for reference if anybody else has the same problem.

I fixed the query by adding 0+ to the line with the string problem.

Like this:

SELECT
UNIX_TIMESTAMP(timestamp) as time_sec,
0+ data as value,
topic as metric
FROM mqtt
WHERE $__timeFilter(timestamp) and ‘temperatur/innetemp’ in(topic)
ORDER BY timestamp ASC