【TDengine 常用的SQL查询介绍】_tdengine twa

作者：小小林熬夜学编程 | 2024-03-10 13:26:55

踩

tdengine twa

[root@localhost ~]# taos

Welcome to the TDengine shell from Linux, Client Version:2.4.0.20
Copyright (c) 2022 by TAOS Data, Inc. All rights reserved.

taos> create database demo;
Query OK, 0 of 0 row(s) in database (0.303909s)

taos> use demo;
Database changed.

taos> create table t (ts timestamp, speed int);
Query OK, 0 of 0 row(s) in database (0.958404s)

taos> insert into t values ('2019-07-15 00:00:00', 10);
Query OK, 1 of 1 row(s) in database (0.002172s)

taos> insert into t values ('2019-07-15 01:00:00', 20);
Query OK, 1 of 1 row(s) in database (0.000878s)

taos> select * from t;
ts | speed |
========================================
2019-07-15 00:00:00.000 | 10 |
2019-07-15 01:00:00.000 | 20 |
Query OK, 2 row(s) in set (0.024162s)

taos> select count(*) from t;
count(*) |
========================
2 |
Query OK, 1 row(s) in set (0.001042s)

taos> SHOW VARIABLES;
name | value |
=====================================
walFlushSize | 1024 |
smlTagNullName | _tag_null |
smlChildTableName | |
defaultJSONStrType | nchar |
clientMerge | 0 |
deadLockKillQuery | 1 |
version | 2.4.0.20 |
buildinfo | Built at 2022-05-15 02:46 |
gitinfoOfInternal | NULL |
gitinfo | 84e1ed5dc6f9fdb457d0acad78a... |
httpDbNameMandatory | 0 |
telegrafUseFieldNum | 0 |
topicBinaryLen | 16000 |
stream | 1 |
monitor | 1 |
mqtt | 0 |
http | 1 |
adjustMaster | 1 |
slaveQuery | 1 |
flowctrl | 1 |
mnodeEqualVnodeNum | 4 |
minimalDataDirGB | 2.000000 |
minimalTmpDirGB | 1.000000 |
minimalLogDirGB | 1.000000 |
maxConnections | 5000 |
maxShellConns | 50000 |
charset | UTF-8 |
locale | zh_CN.UTF-8 |
timezone | (CST, +0800) |
keepColumnName | 1 |
retrieveBlockingModel | 0 |
queryBufferSize | -1 |
maxNumOfOrderedRes | 1000000 |
maxRegexStringLen | 128 |
maxWildCardsLength | 100 |
maxSQLLength | 1048576 |
compressColData | -1 |
compressMsgSize | 524288 |
cachelast | 0 |
update | 0 |
quorum | 1 |
partitions | 4 |
replica | 1 |
fsync | 3000 |
walLevel | 1 |
comp | 2 |
precision | 0 |
maxRows | 4096 |
minRows | 100 |
keep | 3650 |
days | 10 |
blocks | 6 |
cache | 16 |
tableIncStepPerVnode | 1000 |
minTablesPerVnode | 1000 |
maxTablesPerVnode | 1000000 |
maxVgroupsPerDb | 0 |
streamCompDelayRatio | 0.100000 |
retryStreamCompDelay | 10000 |
maxFirstStreamCompDela | 10000 |
maxStreamCompDelay | 20000 |
minIntervalTime | 1 |
minSlidingTime | 10 |
statusInterval | 1 |
offlineThreshold | 864000 |
monitorReplica | 1 |
maxTmrCtrl | 512 |
keepTimeOffset | 0 |
offlineInterval | 3 |
balanceInterval | 300 |
balance | 0 |
syncCheckInterval | 1500 |
tcpConnTimeout | 1000 |
telemetryReporting | 1 |
vnodeBak | 1 |
numOfMnodes | 1 |
maxNumOfDistinctRes | 10000000 |
arbitrator | |
Query OK, 78 row(s) in set (0.003062s)

taos> SHOW TABLES;
table_name | created_time | columns | stable_name | uid | tid | vgId |
=====================================================
t | 2022-06-02 13:39:35.802 | 2 | | 844424946917299 | 1 | 3 |
Query OK, 1 row(s) in set (0.004992s)

taos> SHOW CREATE TABLE t;
Table | Create Table |
==================================================================
t | CREATE TABLE `t` (`ts` TIME... |
Query OK, 1 row(s) in set (0.000328s)

taos> SELECT CLIENT_VERSION();
client_version() |
===================
2.4.0.20 |
Query OK, 1 row(s) in set (0.000285s)

taos> SELECT DATABASE();
database() |
=================================
demo |
Query OK, 1 row(s) in set (0.000238s)

taos> SELECT SERVER_VERSION();
server_version() |
===================
2.4.0.20 |
Query OK, 1 row(s) in set (0.000170s)

TWA功能说明：时间加权平均函数。统计表中某列在一段时间内的时间加权平均。

taos> SELECT TWA(speed) FROM t;
twa(speed) |
============================
15.000000000 |
Query OK, 1 row(s) in set (0.001576s)

IRATE功能说明：计算瞬时增长率。使用时间区间中最后两个样本数据来计算瞬时增长速率；如果这两个值呈递减关系，那么只取最后一个数用于计算，而不是使用二者差值。

taos> SELECT irate(speed) FROM t;
irate(speed) |
============================
0.002777778 |
Query OK, 1 row(s) in set (0.001042s)

STDDEV功能说明：统计表中某列的均方差。

taos> SELECT STDDEV(speed) FROM t;
stddev(speed) |
============================
5.000000000 |
Query OK, 1 row(s) in set (0.001167s)

taos>

声明：本文内容由网友自发贡献，不代表【wpsshop博客】立场，版权归原作者所有，本站不承担相应法律责任。如您发现有侵权的内容，请联系我们。转载请注明出处：https://www.wpsshop.cn/w/小小林熬夜学编程/article/detail/218073