时间戳与 python mysql.connector 的比较

Question

I'm trying to do a timestamp comparison with mysql.connector in Python3. For some reason I've got an empty result with the following query:

SELECT timestamp, reading, value FROM history where device='dht22' and timestamp > now() - interval 6 hour

If I switch the operator to "<" the query works and shows all the results, older than 6 hours ago, but it's not what I want. I want to show the results from the past 6 hours only.

If I execute the query directly in mysql, it works as expected, but in python it doesn't. How can I go around this?

My current python code is like so:

import mysql.connector

cnx = mysql.connector.connect(user='user', password='pass',
                              host='127.0.0.1',
                              database='db')
cur = cnx.cursor()

query="SELECT `timestamp`, `reading`, `value` FROM history where device='dht22' and `timestamp` > now() - interval 6 hour"

cur.execute(query)

rows=cur.fetchall()

for row in rows:
    print(row)

cur.close()
cnx.close()

[UPDATE] I found the problem. I was connecting to the MySQL server though "localhost" and for some reason (bad configuration probably), it was not parsing timestamp comparison correctly. When I put the full domain name in the connection object, all works fine. Really weird!

Answer 1

use BETWEEN

SELECT `timestamp`, reading, value FROM history WHERE device='dht22' AND `timestamp` BETWEEN NOW() - INTERVAL 6 hour AND NOW()

 create table history( id int primary key, reading int, value varchar(19), device VARCHAR(10), `timestamp` datetime ); INSERT INTO history VALUES (1,1,'test','dht22', NOW() - INTERVAL 5 HOUR) ,(2,1,'test','dht22', NOW() - INTERVAL 2 HOUR) ,(3,1,'test','dht22', NOW() - INTERVAL 7 HOUR)

 SELECT `timestamp`, reading, value FROM history WHERE device='dht22' AND `timestamp` BETWEEN NOW() - INTERVAL 6 hour AND NOW()

\ntimestamp | reading | value\n:------------------ |  ------: |  :---- \n2020-08-23 14:30:04 |  1 |  test \n2020-08-23 17:30:04 |  1 |  test \n

db<>fiddle here

See

And also my select