0

I'm trying to use an SQLite query to calculate when an alarm should become active. I store the start time and the detent (the timeout or delay before the alarm becomes active) in the same table as seconds. Here is the schema:

CREATE TABLE alarm_log (
 scope integer NOT NULL, --REFERENCES scopes_inst(inst)
 start integer NOT NULL, -- seconds
 end integer,
 severity text NOT NULL,
 value text NOT NULL,
 details text,
 raised_by integer,      -- the scope id that raised the alarm
 detent integer,         -- detent in seconds
 PRIMARY KEY (scope, start)
);

And here is the query that I am trying to use to pull the active alarms using some simple math:

SELECT *,
  (start + detent) AS activated, -- the time that the alarm becomes active
  STRFTIME("%s","now") AS now    -- the current time of the query
FROM alarm_log 
WHERE end IS NULL
AND now > activated;             -- ensure that the alarm is activated

I have created an alarm with a detent of 30 seconds. The start time is 1378870712 so it should become active at 1378870742 (see the activated column).

This is an example of the above query returning rows 4 seconds before the activated time...

scope       start       end         severity    value                  details           raised_by   detent      activated   now       
----------  ----------  ----------  ----------  ---------------------  ----------------  ----------  ----------  ----------  ----------
4           1378870712              warning     out-of-range too-high  min 500 max 1500  0           30          1378870742  1378870738

Now the same query returns that row 2 seconds after the alarm was activated.

scope       start       end         severity    value                  details           raised_by   detent      activated   now       
----------  ----------  ----------  ----------  ---------------------  ----------------  ----------  ----------  ----------  ----------
4           1378870712              warning     out-of-range too-high  min 500 max 1500  0           30          1378870742  1378870744

I would expect reversing the > on the last line to a < it should show alarms that are not active... but this returns nothing, before or after a detent time passes...

Is this normal behaviour? The query looks fine to me. Thanks for reading :)

EDIT:

I should have mentioned that I also tried it with the calculations straight in the WHERE clause, but it does the same thing :(

SELECT *,
  (start + detent) AS activated, -- the time that the alarm becomes active
  STRFTIME("%s","now") AS now    -- the current time of the query
FROM alarm_log 
WHERE end IS NULL
AND STRFTIME("%s","now") > (start + detent);

EDIT2:

Here's some test data:

SQLite styles:

scope|start|end|severity|value|details|raised_by|detent
4|1378935271|1378935842|warning|out-of-range too-high|min 500 max 1500|0|600
4|1378935854|1378935876|warning|out-of-range too-high|min 500 max 1500|0|600
4|1378935884||warning|out-of-range too-high|min 500 max 1500|0|600

CSV styles

scope,start,end,severity,value,details,raised_by,detent
4,1378935271,1378935842,warning,out-of-range too-high,min 500 max 1500,0,600
4,1378935854,1378935876,warning,out-of-range too-high,min 500 max 1500,0,600
4,1378935884,,warning,out-of-range too-high,min 500 max 1500,0,600
4

1 回答 1

1

尝试这个：

select * from (
  select *, (start + detent) as activated,
    strftime("%s","now") as now
  from alarm_log where end is null
) where cast(now as int) > activated;
于 2013-09-11T05:18:32.707 回答