kdb+ and q
Q+A on all things kdb+ database and the q language
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Floating point precision error

Hi all,I have encountered floating point precision error.( e.g. 0.1-0.1 !=0, or 0.2 - 0.1 != 0.1)Understand floating point error is a known issue for floats in many languages.May I know is there any ways to work around it like the 'decimal' data type...

junocaj by New Contributor
  • 2 replies
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Pick the first row from a table and update a particular value

Hi all,I am new to q, I have a question about updating a keyed table.I have a keyed table with OrderID as key, and with some columns (e.g. price, quantity, time)The table can be huge, containing at least 100,000 rows.I am designing an operation to pi...

junocaj by New Contributor
  • 9 replies
  • 0 kudos

update splayed table on disk

Hi All,I am trying to do an on disk update for a splayed table something on the lines of https://code.kx.com/q/ref/lists/#amendBut it keeps on throwing me an 'open error while I use the filehandle for update.Ex:@[`:tbl;enlist 2;:;dict]where dict is t...

MS1 by New Contributor
  • 2 replies
  • 0 kudos

cannot open up q.exe via cmd

Hello,I downloaded windows.zip file, extracted the contents somewhere and tried launching q via cmd. Result is as per screenshot 1. I also tried setting setx QHOME and setx PATH then launch q but it failed. I went to check the q folder and realized t...

conditional join

Hi,how can I perform a conditional join in q ?I am looking for the q equivalent of the sql: select * from t1, t2 where t1.date < t2.date and t1.number1 < t2.number1 and t1.number2 < t2.number2The only idea I have is to perform a full join and then fi...

laue by New Contributor
  • 7 replies
  • 0 kudos