Manage databases

openGeminiAbout 1 minAbout 364 words

CREATE DATABASE

Syntax

CREATE DATABASE <database_name> [WITH [DURATION <duration>] [REPLICATION <n>] [SHARD DURATION <duration>] [INDEX DURATION <duration>] [NAME <retention-policy-name>]]

<database_name>

represents the db name

DURATION <duration>

represents how long the data keeps in openGemini, which is one of the attributes of the data retention policy

SHARD DURATION <duration>

represents the time range of each shard in a shardGroup

INDEX DURATION <duration>

represents the time range of indexGroup

WITH, DURATION, REPLICATION, SHARD DURATION, INDEX DURATION, NAME clauses and creating a single retention policy associated with the database are optional. If no clause is specified after WITH, a retention policy named autogen is created by default.

There does not return any information when execute the command create database or repeated execute the command.

Examples

Create database

> CREATE DATABASE "NOAA_water_database"

This query creates a database named NOAA_water_database.

By default, openGemini also creates the default retention policy autogen and associates it with the database NOAA_water_database.

Create a database with specific retention policies

> CREATE DATABASE "NOAA_water_database" WITH DURATION 3d REPLICATION 1 SHARD DURATION 1h INDEX DURATION 7h NAME "rp3d"

This operation creates a database with the name NOAA_water_database. It also creates a default retention policy for NOAA_water_database with the name rp3d, data is kept in the database for 3 days, data replication is 1, and the time range for each shard is 1 hour, and the time range for index group is 7 hours.

Special case

When using the tag array function, the statement to create the database is as follows:

>create database NOAA_water_database tag attribute array

related entries Retention policy

SHOW DATABASES

Returns a list of all databases in openGemini.

Syntax

SHOW DATABASES

Examples

> SHOW DATABASES
name: databases
+---------------------+
| name                |
+---------------------+
| NOAA_water_database |
+---------------------+
1 columns, 1 rows in set

openGemini has one database: NOAA_water_database.

DROP DATABASE

DROP DATABASE will drop a database and removes all database's data include measurements, series, continuous queries, and retention policies.

Syntax

DROP DATABASE <database_name>

Examples

delete db 'NOAA_water_database'

> DROP DATABASE "NOAA_water_database"

DROP DATABASE returns no results when the command excution successful. openGemini will not return an error if you delete a non-existing database.