I have an Influxdb with lots of fields and a single tag:
> show tag keys
name: rtl433
tagKey
------
model
Now, I want a list of all possible values for model, so I run
SELECT model FROM rtl433
>
-and it returns nothing. Why? There's lots of data in model if I select *.
You are trying to use classic SQL solution, but InfluxDB is not classic SQL DB. You should check InfluxDB doc and you will find solution:
SHOW TAG VALUES WITH KEY = "model"
Related
TL;DR
How to model data into fields vs tags incase you want to perform both group by and count(distinct())
So currently this is my influxdb data model:
api_requests (database)
- requests_stats (measurement)
- api_path (tag)
- app_version (tag)
- host (tag)
- platform (tag)
- account_id (field)
- user_id (field)
- function_name (field)
- network (field)
- network_type (field)
- time_to_execute (field)
So now I want to find out the number of distinct accounts (active accounts).
So I can run the following query:
SELECT count(distinct("account_id")) AS "active_accounts"
FROM "api_requests"."autogen"."requests_stats"
This works fine as account id is a field.
Now suppose I want to perform a group by operation on account_id, for example to find the number of requests received per account:
SELECT count("function_name") AS "request_count"
FROM "api_requests"."autogen"."requests_stats"
GROUP BY "account_id"
I cannot do this as group by is recommended on tags.
How would one manage this kind of scenerio?
One of the solution is to store the value in both field and value but that would be data redundancy.
The other and the most optimal way would be for count(distinct()) to work on tags. Is this possible? This was actually a feature request in their github repo.
Or can something be done about the data model to achieve the same?
Use tag for account_id. Instead of count query:
SELECT count(distinct("account_id")) AS "active_accounts"
FROM "api_requests"."autogen"."requests_stats"
use query, which will calculate exact tag value cardinality:
SHOW TAG VALUES EXACT CARDINALITY WITH KEY = "account_id"
This will work only for your use case, because you don't want to use any additional (time, tag) filter in your distinct count query.
I want to retrieve data in Delphi using a stored procedure. I used the below SQL statement and Initial as a parameter:
SELECT * FROM "PackUser" where Initials in (:Initial)
It didn't select any records when the user types A,B in my Edit box, because it sends a single string 'A,B' to the stored procedure. I want to add extra quotes in the middle: 'A','B'.
How can I do this?
This can be done like this:
input_string=',A,B,C.D'
SELECT * FROM "PackUser" where locate(concat(',', Initials), input_string);
I am a beginner with InfluxDB and I've read the intro documentation, but cannot find any details on how to create a new measurement. Am I missing something ?
As noted in the comments, to "create" a new measurement you simply insert data into that measurement.
For example
$ influx
> CREATE DATABASE mydb
> USE mydb
Using database mydb
> SHOW MEASUREMENTS
> INSERT cpu,host=serverA value=10
> SHOW MEASUREMENTS
name: measurements
name
----
cpu
> INSERT mem,host=serverA value=10
> SHOW MEASUREMENTS
name: measurements
name
----
cpu
mem
In INFLUX DB , you cant create empty measurements.
You need to add some data as well.
For Example,
INSERT xyz,name=serverA value=10,count=10
This will create a measurement name xyz where
tag keys : name
field keys : value & count
You can check Field and tag keys by executing show field keys or show tag keys.
In the INSERT command, the format is like :
measurement_name,tag keys + value separated by comma Field keys with value separated by comma
eg: INSERT xyz,name=serverA value=10,count=10
In this way, you can create measurement with specifying your required field and tag keys.
You cannot create an empty measurement, afaik.
Like they said above, if you want one you need to start writing to it and that should take care of creating one along with some data in it.
insert load,app_name=app3,groupname=second,performance=degraded uuid=003,loading=50,frequency=1
In the above, we are using "insert" to write new data into a new measurement called "load".
app_name,groupname,performance are 'tags' and uuid,loading,frequency are fields
create database <data base name of your choice>
create user "<username>" with password '<password>'
To see the all databases: SHOW DATABASES
Enter the Database: use <database name>
To see all tables inside the database: SHOW MEASUREMENTS
grant all on <data base name> to <username>
insert data (Here Motionsense is a Measurement which is similar to the table name of SQL): INSERT MotionSense,SensorType=Gyro roll=1.2,yaw=5,pitch=3
See the data of the Measurements: SELECT * FROM "MotionSense"
I'm searching a way to simulate "create table as select" in Firebird from SP.
We are using this statement frequently in another product, because it is very easy for make lesser, indexable sets, and provide very fast results in server side.
create temp table a select * from xxx where ...
create indexes on a ...
create temp table b select * from xxx where ...
create indexes on b ...
select * from a
union
select * from b
Or to avoid the three or more levels in subqueries.
select *
from a where id in (select id
from b
where ... and id in (select id from c where))
The "create table as select" is very good cos it's provide correct field types and names so I don't need to predefine them.
I can simulate "create table as" in Firebird with Delphi as:
Make select with no rows, get the table field types, convert them to create table SQL, run it, and make "insert into temp table " + selectsql with rows (without order by).
It's ok.
But can I create same thing in a common stored procedure which gets a select sql, and creates a new temp table with the result?
So: can I get query result's field types to I can create field creator SQL from them?
I'm just asking if is there a way or not (then I MUST specify the columns).
Executing DDL inside stored procedure is not supported by Firebird. You could do it using EXECUTE STATEMENT but it is not recommended (see the warning in the end of "No data returned" topic).
One way to do have your "temporary sets" would be to use (transaction-level) Global Temporary Table. Create the GTT as part of the database, with correct datatypes but without constraints (those would probably get into way when you fill only some columns, not all) - then each transaction only sees it's own version of the table and data...
I'm using Rails to get data from Postgresql by passing dynamic column and table name.
I cannot use ActiveRecord because the shape data that is imported from shapefile is dynamic both table and column name.
I have to use double quote with a column name in the query to avoid problem such column name: "addr:city" for example.
def find_by_column_and_table(column_name, shape_table_name)
sql = "SELECT \"#{column_name}\" FROM \"#{shape_table_name}\" WHERE \"#{column_name}\" IS NOT NULL"
ActiveRecord::Base.connection.select_one(sql)
end
2 examples of generated sql statement:
SELECT "place" FROM "shp_6c998258-32a6-11e0-b34b-080027997e00"
SELECT "addr:province" FROM "shp_6c998258-32a6-11e0-b34b-080027997e00"
I want to make sure there is no sql injection in the query.
Could anyone point me how to solve this issue?
The recommended way to prevent injection, speed up your query and catch errors is to use positional parameters or stored proceedures. Anything less is asking for trouble.
http://nasir.wordpress.com/2007/12/03/stored-procedures-and-rails/
http://www.postgresql.org/docs/9.0/static/sql-expressions.html#AEN1834