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General SQL Statements

About 2 min

General SQL Statements

Database Management

Database is similar to the database in the relational database, which is a collection of structured time series data.

create database

Create a database named root.ln with the following syntax:

CREATE DATABASE root.ln

show databases

View all databases:

SHOW DATABASES

delete database

Drop the database named root.ln:

DELETE DATABASE root.ln

count databases

COUNT DATABASES

Time Series Management

Time series is a collection of data points indexed by time. In IoTDB, time series refers to a complete sequence of measurement points. This section mainly introduces the management of time series.

create timeseries

The encoding method and data type need to be specified. For example, create a time series named root.ln.wf01.wt01.temperature:

CREATE TIMESERIES root.ln.wf01.wt01.temperature WITH datatype=FLOAT,ENCODING=RLE

show timeseries

View all time series:

SHOW TIMESERIES

Use wildcards to match time series under database root.ln:

SHOW TIMESERIES root.ln.**

delete timeseries

Delete a time series named root.ln.wf01.wt01.temperature:

DELETE TIMESERIES root.ln.wf01.wt01.temperature

count timeseries

Count the total number of time series:

COUNT TIMESERIES root.**

Count the number of time series under a wildcard path:

COUNT TIMESERIES root.ln.**

Time Series Path Management

In addition to the concept of time series, IoTDB also has the concepts of subpaths and devices.

Subpath: It is a part of the path in a complete time series name. For example, if the time series name is root.ln.wf01.wt01.temperature, then root.ln, root.ln.wf01, and root.ln.wf01.wt01 are all its subpaths.

Device: It is a combination of a group of time series. In IoTDB, the device is a subpath from the root to the penultimate node. If the time series name is root.ln.wf01.wt01.temperature, then root.ln.wf01.wt01 is its device.

show devices

SHOW DEVICES

show child paths

Check out the next level of root.ln:

SHOW CHILD PATHS root.ln

show child nodes

SHOW CHILD NODES root.ln

count devices

Count the number of devices:

COUNT DEVICES

count nodes

Count the number of nodes at the specified level in the path:

COUNT NODES root.ln.** LEVEL=2

Query Data

The following are commonly used query statements in IoTDB.

Query the data of the specified time series

Query all time series data under the device root.ln.wf01.wt01:

SELECT * FROM root.ln.wf01.wt01

Query time series data within a certain time range

Query the data in the time series root.ln.wf01.wt01.temperature whose timestamp is greater than 2022-01-01T00:05:00.000:

SELECT temperature FROM root.ln.wf01.wt01 WHERE time > 2022-01-01T00:05:00.000

Query time series data whose values are within the specified range

Query the data whose value is greater than 36.5 in the time series root.ln.wf01.wt01.temperature:

SELECT temperature FROM root.ln.wf01.wt01 WHERE temperature > 36.5

Use last to query the latest point data

SELECT last * FROM root.ln.wf01.wt01

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