Solved

What is wrong with this MySQL statement?

Posted on 2011-09-17
7
324 Views
Last Modified: 2012-05-12
The statement below does not give an error code, but it does not compute the TIMEDIFF:

"UPDATE Stop_times, Start_times
SET Stop_times.Project_Charge_Time=TIMEDIFF(Stop_times.STOPid,Start_times.STARTid)
WHERE Start_times.PROJECTid = Stop_times.PROJECTid
AND
Start_times.EMPLOYid=Stop_times.EMPLOYid"

but if you delete the update and modify it to a select statement like '/**UPDATE Stop_times, Start_times
SET Stop_times.Project_Charge_Time=/**/  SELECT TIMEDIFF(Stop_times.STOPid,Start_times.STARTid)
FROM Stop_times, Start_times
WHERE Start_times.PROJECTid = Stop_times.PROJECTid
AND
Start_times.EMPLOYid=Stop_times.EMPLOYid

it computes the time difference correctly
0
Comment
Question by:ToreJohn
  • 4
  • 3
7 Comments
 
LVL 59

Expert Comment

by:Kevin Cross
ID: 36554322
Hi. You said it does not throw an error; therefore, how are you judging that it did not compute?
0
 
LVL 59

Expert Comment

by:Kevin Cross
ID: 36554337
The syntax you have looks fine, so suspect something else. For example, by naming convention, I would not expect the actual time values to be in a column STARTid or STOPid. When I see that I think AUTO_INCREMENT or INT fields that are keys to a table. Try the below syntax ensuring that the columns in TIMEDIFF are indeed DATETIME columns. Since you said this works in SELECT, that may be the STARTid and STOPid, but may be worth double checking.

UPDATE Stop_times stp
JOIN Start_times strt 
    ON strt.PROJECTid = stp.PROJECTid
   AND strt.EMPLOYid = stp.EMPLOYid
SET stp.Project_Charge_Time = TIMEDIFF(stp.STOPdatetime, strt.STARTdatetime)
;

Open in new window

0
 

Author Comment

by:ToreJohn
ID: 36554366
I can see that it does not work because stp.Project_Charge_Time is 0000-00-00 00:00:00 also after running the query. Your alternative code gives the same result. (When I modified stp.STOPdatetime to STOPid and the same for STARTid)
0
The Eight Noble Truths of Backup and Recovery

How can IT departments tackle the challenges of a Big Data world? This white paper provides a roadmap to success and helps companies ensure that all their data is safe and secure, no matter if it resides on-premise with physical or virtual machines or in the cloud.

 
LVL 59

Expert Comment

by:Kevin Cross
ID: 36554372
Wait. Project_Charge_Time is a datetime?
Remember TIMEDIFF is given you a difference in time values. It is not resulting in a datetime value. Please show the table structure(s) and some sample data with what you expect the final results to be.
0
 

Author Comment

by:ToreJohn
ID: 36554431
Yes and Thanks.
I used datetime as the format for the output. Changing the format did the trick
0
 
LVL 59

Accepted Solution

by:
Kevin Cross earned 500 total points
ID: 36554441
You are welcome!
0
 

Author Closing Comment

by:ToreJohn
ID: 36554450
It was fine. He understood that what I had done was correct and pointed me in the right direction.
0

Featured Post

PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

As a database administrator, you may need to audit your table(s) to determine whether the data types are optimal for your real-world data needs.  This Article is intended to be a resource for such a task. Preface The other day, I was involved …
Both Easy and Powerful How easy is PHP? http://lmgtfy.com?q=how+easy+is+php  Very easy.  It has been described as "a programming language even my grandmother can use." How powerful is PHP?  http://en.wikipedia.org/wiki/PHP  Very powerful.  But a…
This Micro Tutorial will teach you how to censor certain areas of your screen. The example in this video will show a little boy's face being blurred. This will be demonstrated using Adobe Premiere Pro CS6.
This video shows how to use Hyena, from SystemTools Software, to bulk import 100 user accounts from an external text file. View in 1080p for best video quality.

825 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question