How can I select database with http query?


I’m making a program which uses Influxdb and this program is made with c++.
And in my program, I use the Curl to process http query.

In my program, I’m trying to select database with http query like this,


But, the Influxdb returns HTTP status code, 400.
And the error message, returned as json format, is as follows:

"{\"error\":\"error parsing query: found USE, expected SELECT, DELETE, SHOW, CREATE, DROP, EXPLAIN, GRANT, REVOKE, ALTER, SET, KILL at line 1, char 1\"}\n".

I have checked if the Influxdb is working properly with “influx.exe” in the command line.
The results is shown below. As can be see, Influxdb is working well.
(the “my_database” is “tick_data”.)

Microsoft Windows [Version 10.0.17134.590]
(c) 2018 Microsoft Corporation. All rights reserved.

D:\Program Files (x86)\influxdb\1.5.2-1>influx
Connected to http://localhost:8086 version 1.5.2
InfluxDB shell version: 1.5.2
> show databases
name: databases
> use tick_data
Using database tick_data

Could anybody tell me what is problem of my http query?


I don’t think you need to specify “USE DB NAME”.

curl -G 'http://localhost:8086/query?db=mydb' --data-urlencode 'q=SELECT * FROM "mymeas"'

You specify it as the value for the db part of the URL.


Thank you for your reply.
Yes, your answer is enough to resolve my question.

But I just want to know why my http query does not work.
And I also want to know if it is possible to select a database with “use” command.

Using Curl program in command line in the Window 10, I have tried another http query like this,

curl -XPOST "http://localhost:8086/query" --data-urlencode "q=CREATE DATABASE "test_9999"",

and this works. I could check that the database “test_9999” was created.
After seen this query, I thought that the syntax of my previous http query could be wrong.
So I tried modified http query like this,

curl -XPOST "http://localhost:8086/query" --data-urlencode "q=USE "tick_data"".

But it also does not work as I expected.


I’m not sure if “USE” is valid syntax for the http query. To be honest though I’m not 100% sure about that.

It looks as though /query?db=database_name is the equivilant of specifying USE in the query. So instead of

curl -XPOST "http://localhost:8086/query" --data-urlencode "q=USE "tick_data""

you would just specify

curl -XPOST "http://localhost:8086/query?db=database" --data-urlencode "q=SELECT * "tick_data""

In short, i don’t think you can select the database with USE through http.

Not sure if that helps, it might be worth tagging one of the forum support staff for better clarification.


Thank you for your reply.


use is not part of InfluxQL, it is a command provided by the CLI to set the database and retention policy:

use [ "<database_name>" | "<database_name>"."<retention policy_name>" ] Sets the current database and/or retention policy. Once influx sets the current database and/or retention policy, there is no need to specify that database and/or retention policy in queries. If you do not specify the retention policy, influx automatically queries the use d database’s DEFAULT retention policy.

In InfluxQL, the FROM clause provides several formats for specifying a measurement, including “fully qualified” measurements, which allow you to specify which database and retention policy the query should use:

FROM <database_name>.<retention_policy_name>.<measurement_name> Returns data from a fully qualified measurement. Fully qualify a measurement by specifying its database and retention policy.

Setting the database in an HTTP request using query parameters is also valid, and is documented in the /query endpoint docs under Query string parameters.


Your reply is very helpful.
Thank you very much.

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