I have a following issue:
I need to calculate difference between consecutive points where some arbitrary ID is equal. The following:
SELECT difference(value_field) FROM mesurementName WHERE "IdField" = '10'
Works, returns difference between each consecutive point with IdField BUT IdField is lost (only time is propagated to query result). In my case time is not unique (i.e. measurement may contain many points with same timestamp, but different IdField). So I tried:
SELECT difference(value_field), IdField FROM mesurementName WHERE "IdField" = '10'
which yields:
error parsing query: mixing aggregate and non-aggregate queries is not supported!!
My next attempt was using sub-query:
SELECT IdField, diff
FROM (
SELECT
difference(flow_val) as diff
FROM
mesurementA
WHERE "IdField" = '10'
)
Which resulted in always null value in IdField.
I'd like to ask you for help or suggestion how to solve issue. By the way, we are using InfluxDB 1.3, which is not supporting JOIN anymore
If anyone would stuck as I was, then solution is following:
SELECT difference(value_field) FROM mesurementName GROUP BY "IdField"
Above somehow implicitly add "IdField" to result series and is propagated to resulting measurements with INTO clause
Related
I was trying to write a simple FluxQL Query in Grafana Dashboard that uses a variable
m1(of type constant)(which contains the name of the measurement)
I created the variable m1 in grafana dashboard variables
m1 = my-measurement
and tried to run the following queries but non of them worked and they either say expression request error or No Data)
i.e
SELECT count("fails") FROM "/^${m1:raw}$/"
SELECT count("fails") FROM "/^${m1}$/"
SELECT count("fails") FROM $m1" (expression request error)
SELECT count("fails") FROM "$m1"
SELECT count("fails") FROM "${m1}"
The only query worked was without dashboard variables
SELECT count("fails") FROM "my-measurement"
How can I use the variables to work for that query.
On the similar ground I tried to make a custom variable(myVar) for which we take integer input values from user and on that basis where clause should work, but same error occurs either no data or expression request error
What I tried was
SELECT count(*) from "my-measurement-2" WHERE ("value" > $myVar)
How should I solve these issues?Please help
You may have a problem with
1.) syntax
SELECT count("fails")
FROM "${m1:raw}"
2.) data
You may correct query syntax, but query can be very inefficient. Query execution may need a lot of time - so it's better to have timefilter, which will use selected dashboard time range (make sure you have some data in that time range)
SELECT count("fails")
FROM "${m1:raw}"
WHERE $timeFilter
3.) Grafana panel configuration
Make sure you are using suitable panel - for query above Stat panel is a good option (that query returns only single value, not timeseries, so time series panel types may have a problem with that).
Generally, use query inspector to see how are variables interpolated - there can be "magic", which is not obvious - e.g. quotes which are added around numeric variables, so then it is string filtering and not numeric filtering on the InfluxDB level.
I wanna update my table for all persons whoes activity lasted toooo long. The update should correct one time and for the subsequent rows I need to deal with new result. So thought about something like
UPDATE summary_table st
SET st.screen_on=newScreenOnValue
st.active_screen_on=st.active_screen_on-(st.screen_on-newScreenOnValue) --old-value minus thedifference
FROM (
SUB-SELECT with rowid, newScreenOnValue ... JOIN ... WHERE....
) nv
WHERE (st.rowid=nv.rowid)
I know that I can update the first and the second value directly, by rerunning the same query. But my problem is the costs of the subselect seems quite high and therefore wanna avoid a double-update resp. double-run of the same query.
The above SELECT is just a informal way of writting what I think I would like to get. I know that the st doesn't work, but I left it here for better understanding. When I try the above statement I always get back a SyntaxError at the position the FROM ends.
This can be achieved as follows:
UPDATE summary_table st
SET (st.screen_on, st.active_screen_on) =
((SELECT newScreenOnValue, st.active_screen_on-(st.screen_on-newScreenOnValue)
FROM ...
JOIN...
WHERE..))
[WHERE if any additional condition required];
The above query works perfectly fine on informix tried and tested until you make any errors in the FROM, JOIN, WHERE clauses.
Cheers !
Syntax error because a comma is missing between the first and second columns you're updating.
Never use ROWID's, they're volatile and also not used by default with IDS, unless you specify so.
Why are you using a subquery?
I have a table with almost 300K records in it. I run a simple select statement with a where clause on an indexed column ('type' is indexed):
SELECT *
FROM Asset_Spec
WHERE type = 'County'
That query is fast - about 1 second. Additionally I want to test against status:
SELECT *
FROM Asset_Spec
WHERE type = 'County'
AND status = 'Active'
The second one is VERY slow (minutes). Status is NOT indexed and in this particular case 99.9% of values in the db ARE 'Active'.
Any ideas how I can get better performance? We are compiling our own version of SQLite so I can tweak many settings (FYI - same performance on iOS pre-canned SQLite)
I looked at the query plan and the estimate for number of rows was off by an astounding amount. Asset_Spec (~2 rows) - actual number of rows is almost 300,000. Ran 'ANALYZE' - now the same query runs in 16ms.
the first thing I would try is using a subquery
SELECT * FROM
(SELECT *
FROM Asset_Spec
WHERE type = 'County')
WHERE status = 'Active'
and as Robert suggests, adding an index on any column you want to filter by is a good idea. I'd also consider changing fields Type and Status to be something other than string.
Any reason you need to select *?
Suggestions:
Do you need to retrieve multiple records? If all you need is the first record found, then add "limit 1" to the end of the query.
If you're just checking for the existence of a row, i.e. you only need to know that there is one row with status active, then "select 1" instead of "select *".
Ruby 1.9.2 / rails 3.1 / deploy onto heroku --> posgresql
Hi, Once a number of rows relating to an object goes over a certain amount, I wish to pull back every nth row instead. It's simply because the rows are used (in part) to display data for graphing, so once the number of rows returned goes above say 20, it's good to return every second one, and so forth.
This question seemed to point in the right direction:
ActiveRecord Find - Skipping Records or Getting Every Nth Record
Doing a mod on row number makes sense, but using basically:
#widgetstats = self.widgetstats.find(:all,:conditions => 'MOD(ROW_NUMBER(),3) = 0 ')
doesn't work, it returns an error:
PGError: ERROR: window function call requires an OVER clause
And any attempt to solve that with e.g. basing my OVER clause syntax on things I see in the answer on this question:
Row numbering in PostgreSQL
ends in syntax errors and I can't get a result.
Am I missing a more obvious way of efficiently returning every nth task or if I'm on the right track any pointers on the way to go? Obviously returning all the data and fixing it in rails afterwards is possible, but terribly inefficient.
Thank you!
I think you are looking for a query like this one:
SELECT * FROM (SELECT widgetstats.*, row_number() OVER () AS rownum FROM widgetstats ORDER BY id) stats WHERE mod(rownum,3) = 0
This is difficult to build using ActiveRecord, so you might be forced to do something like:
#widgetstats = self.widgetstats.find_by_sql(
%{
SELECT * FROM
(
SELECT widgetstats.*, row_number() OVER () AS rownum FROM widgetstats ORDER BY id
) AS stats
WHERE mod(rownum,3) = 0
}
)
You'll obviously want to change the ordering used and add any WHERE clauses or other modifications to suit your needs.
Were I to solve this, I would either just write the SQL myself, like the SQL that you linked to. You can do this with
my_model.connection.execute('...')
or just get the id numbers and find by id
ids = (1..30).step(2)
my_model.where(id => ids)
I have a complex query that contains more than one place where the same primary key value must be substituted. It looks like this:
select Foo.Id,
Foo.BearBaitId,
Foo.LinkType,
Foo.BugId,
Foo.GooNum,
Foo.WorkOrderId,
(case when Goo.ZenID is null or Goo.ZenID=0 then
IsNull(dbo.EmptyToNull(Bar.FanName),dbo.EmptyToNull(Bar.BazName))+' '+Bar.Strength else
'#'+BarZen.Description end) as Description,
Foo.Init,
Foo.DateCreated,
Foo.DateChanged,
Bug.LastName,
Bug.FirstName,
Goo.BarID,
(case when Goo.ZenID is null or Goo.ZenID=0 then
IsNull(dbo.EmptyToNull(Bar.BazName),dbo.EmptyToNull(Bar.FanName))+' '+Bar.Strength else
'#'+BarZen.Description end) as BazName,
GooTracking.Status as GooTrackingStatus
from
Foo
inner join Bug on (Foo.BugId=Bug.Id)
inner join Goo on (Foo.GooNum=Goo.GooNum)
left join Bar on (Bar.Id=Goo.BarID)
left join BarZen on (Goo.ZenID=BarZen.ID)
inner join GooTracking on(Goo.GooNum=GooTracking.GooNum )
where (BearBaitId = :aBaitid)
UNION
select Foo.Id,
Foo.BearBaitId,
Foo.LinkType,
Foo.BugId,
Foo.GooNum,
Foo.WorkOrderId,
Foo.Description,
Foo.Init,
Foo.DateCreated,
Foo.DateChanged,
Bug.LastName,
Bug.FirstName,
0,
NULL,
0
from Foo
inner join Bug on (Foo.BugId=Bug.Id)
where (LinkType=0) and (BearBaitId= :aBaitid )
order by BearBaitId,LinkType desc, GooNum
When I try to use an integer parameter on this non-trivial query, it seems impossible to me. I get this error:
Error
Incorrect syntax near ':'.
The query works fine if I take out the :aBaitid and substitute a literal 1.
Is there something else I can do to this query above? When I test with simple tests like this:
select * from foo where id = :anid
These simple cases work fine. The component is TADOQuery, and it works fine until you add any :parameters to the SQL string.
Update: when I use the following code at runtime, the parameter substitutions are actually done (some glitch in the ADO components is worked around) and a different error surfaces:
adoFooContentQuery.Parameters.FindParam('aBaitId').Value := 1;
adoFooContentQuery.Active := true;
Now the error changes to:
Incorrect syntax near the keyword 'inner''.
Note again, that this error goes away if I simply stop using the parameter substitution feature.
Update2: The accepted answer suggests I have to find two different copies of the parameter with the same name, which bothered me so I reworked the query like this:
DECLARE #aVar int;
SET #aVar = :aBaitid;
SELECT ....(long query here)
Then I used #aVar throughout the script where needed, to avoid the repeated use of :aBaitId. (If the number of times the parameter value is used changes, I don't want to have to find all parameters matching a name, and replace them).
I suppose a helper-function like this would be fine too: SetAllParamsNamed(aQuery:TAdoQuery; aName:String;aValue:Variant)
FindParam only finds one parameter, while you have two with the same name. Delphi dataset adds each parameter as a separate one to its collection of parameters.
It should work if you loop through all parameters, check if the name matches, and set the value of each one that matches, although I normally choose to give each same parameter a follow-up number to distingish between them.