?
Solved

help to understand a SQL update statement with DIGITS and SIGN

Posted on 2010-11-17
3
Medium Priority
?
386 Views
Last Modified: 2012-05-10
I am trying to understand a SQL update statement with an application we use. Can someone break this down and explain what it is doing? It is used on an DB2 database

The output value is always either a 4 digit string (eg '0003') or null.

Update Table1 set fieldA= SUBSTR(DIGITS(N.INPUT)||'####',7+SIGN(SIGN(1-10000)+1)*4,4) Where record = ......

0
Comment
Question by:JDCam
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
3 Comments
 
LVL 46

Accepted Solution

by:
Kent Olsen earned 2000 total points
ID: 34160567
Hi JD,

Easy enough.

The DIGITS function returns an integer value as a string.  The length of the returned string is dependent upon the datatype and is leading zero filled if necessary to ensure that the string is as long as the longest possible string for that type.,

The SIGN function returns -1, 0, or 1, depending on the sign of the argument.

  SUBSTR(DIGITS(N.INPUT)||'####',7+SIGN(SIGN(1-10000)+1)*4,4)

N.INPUT is the only variable in the equation.

If N.INPUT is a short integer (5 digits) with a value of 12, the first parameter to SUBSTR becomes '00012####'.

  7+SIGN(SIGN(1-10000)+1)*4
  7+SIGN(SIGN(-9999)+1)*4
  7+SIGN(-1+1)*4
  7+0*4
  7

So if N.INPUT is 12, the call to SUBSTR becomes

  SUBSTR ('000012####', 7, 4);


It looks like someone deliberately obfuscated some code here.



Good Luck,
Kent
0
 
LVL 1

Author Comment

by:JDCam
ID: 34160702
Wow !! I don't feel so bad for not understanding this one. And if nothing else, I learned A new word today

If we said the the longest possible string is only 4 char. Then would it make sense that the trailing ',4' is intended to output at 4 characters.

Thus input 3 would output 0003 which matches the behavior today.

0
 
LVL 1

Author Closing Comment

by:JDCam
ID: 34163803
Thanks!
0

Featured Post

New benefit for Premium Members - Upgrade now!

Ready to get started with anonymous questions today? It's easy! Learn more.

Question has a verified solution.

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

Confronted with some SQL you don't know can be a daunting task. It can be even more daunting if that SQL carries some of the old secret codes used in the Ye Olde query syntax, such as: (+)     as used in Oracle;     *=     =*    as used in Sybase …
This article describes how to use the timestamp of existing data in a database to allow Tableau to calculate the prior work day instead of relying on case statements or if statements to calculate the days of the week.
This is my first video review of Microsoft Bookings, I will be doing a part two with a bit more information, but wanted to get this out to you folks.
In this video, Percona Solutions Engineer Barrett Chambers discusses some of the basic syntax differences between MySQL and MongoDB. To learn more check out our webinar on MongoDB administration for MySQL DBA: https://www.percona.com/resources/we…
Suggested Courses

770 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