Mastering TDengine: Essential Commands and Tips for IoT Time-Series Data

1. Change User Password

The default password for the root user is taosdata. Change it with:

alter user root pass 'your_password';

2. Login to the Database

Connect using the taos client. Parameters must be concatenated without spaces:

taos -uroot -p123456;

3. Database Operations

Create, select, and drop databases, and adjust their properties:

create database if not exists mydb keep 365 days 10 blocks 4;

use mydb;

drop database mydb;

drop database if exists mydb;

show databases;

alter database mydb comp 2;

alter database mydb replica 2;

alter database mydb keep 365;

alter database mydb quorum 2;

alter database mydb blocks 100;

4. Table Operations

Create regular tables, sub‑tables, and manage columns:

create table if not exists mytable (column_name timestamp, column_name int, ...);

create table table_name using super_table tags (column_value, column_value, ...);

drop table if exists mytable;

show tables;

show tables like "%table_name%";

describe mytable;

alter table mytable add column addfield int;

alter table mytable drop column addfield;

5. Super Table Operations

Super tables store common fields while tags hold device‑specific metadata:

create table if not exists mysupertable (time timestamp, column_name int, ...) tags (column_name nchar(50), column_name nchar(100), ...);

drop table if exists super_table;

show stables like "%super%";

describe super_table;

alter table super_table add column column_name int;

alter table super_table drop column column_name;

alter table super_table add tag column nchar(60);

alter table super_table drop tag tag_name;

alter table super_table change tag old_tag_name new_tag_name;

alter table item_table_name set tag column_key = "value";

6. Relationship Explanation

In an IoT scenario, each electric‑meter device can be represented as a sub‑table of a super table. The measurement fields (current, voltage) are regular columns, while owner name, location, and room number are stored as tags.

7. Practical Example

Creating a super table for electric meters and corresponding sub‑tables:

create database mydb;

use mydb;

create table super_dianbiao (ts timestamp, dianya float, dianliu float) tags (yezhu_name nchar(15), xiaoqu_location nchar(50), menpai_num nchar(10));

create table dianbiao1001 using super_dianbiao tags('张三','东城小区','1-1101');

create table dianbiao1002 using super_dianbiao tags('李四','东城小区','1-1102');

insert into dianbiao1001 values(now,1.7,3.2);