Join IIUG
 for   
 

Informix News
18 Nov 13 - ZDNet - Top 20 mobile skills in demand... Read
09 Sep 13 - telecompaper - Shaspa and Tatung have shown a new smart home platform at Ifa in Berlin. Powered by the IBM Informix software... Read
06 Sep 13 - IBM data magazine - Mission Accomplished - Miami, Florida will be the backdrop for the 2014 IIUG Informix Conference... Read
01 Feb 13 - IBM Data Magazine - Are your database backups safe? Lester Knutsen (IBM Champion) writes about database back up safety using "archecker"... Read
14 Nov 12 - IBM - IBM's Big Data For Smart Grid Goes Live In Texas... Read
3 Oct 12 - The Financial - IBM and TransWorks Collaborate to Help Louisiana-Pacific Corporation Achieve Supply Chain Efficiency... Read
28 Aug 12 - techCLOUD9 - Splunk kicks up a SaaS Storm... Read
10 Aug 12 - businessCLOUD9 - Is this the other half of Cloud monitoring?... Read
3 Aug 12 - IBM data management - Supercharging the data warehouse while keeping costs down IBM Informix Warehouse Accelerator (IWA) delivers superior performance for in-memory analytics processing... Read
2 Aug 12 - channelbiz - Oninit Group launches Pay Per Pulse cloud-based service... Read
28 May 12 - Bloor - David Norfolk on the recent Informix benchmark "pretty impressive results"... Read
23 May 12 - DBTA - Informix Genero: A Way to Modernize Informix 4GL Applications... Read
9 Apr 12 - Mastering Data Management - Upping the Informix Ante: Advanced Data Tools... Read
22 Mar 12 - developerWorks - Optimizing Informix database access... Read
14 Mar 12 - BernieSpang.com - International Informix User Group set to meet in San Diego... Read
1 Mar 12 - IBM Data Management - IIUG Heads West for 2012 - Get ready for sun and sand in San Diego... Read
1 Mar 12 - IBM Data Management - Running Informix on Solid-State Drives.Speed Up Database Access... Read
26 Feb 12 - BernieSpan.com - Better results, lower cost for a broad set of new IBM clients and partners... Read
24 Feb 12 - developerWorks - Informix Warehouse Accelerator: Continuous Acceleration during Data Refresh... Read
6 Feb 12 - PRLOG - Informix port delivers unlimited database scalability for popular SaaS application ... Read
2 Feb 12 - developerWorks - Loading data with the IBM Informix TimeSeries Plug-in for Data Studio... Read
1 Feb 12 - developerWorks - 100 Tech Tips, #47: Log-in to Fix Central... Read
13 Jan 12 - MC Press online - Informix Dynamic Server Entices New Users with Free Production Edition ... Read
11 Jan 12 - Computerworld - Ecologic Analytics and Landis+Gyr -- Suitors Decide to Tie the Knot... Read
9 Jan 12 - planetIDS.com - DNS impact on Informix / Impacto do DNS no Informix... Read
8 Sep 11 - TMCnet.com - IBM Offers Database Solution to Enable Smart Meter Data Capture... Read
1 Aug 11 - IBM Data Management Magazine - IIUG user view: Happy 10th anniversary to IBM and Informix... Read
8 Jul 11 - Database Trends and Applications - Managing Time Series Data with Informix... Read
31 May 11 - Smart Grid - The meter data management pitfall utilities are overlooking... Read
27 May 11 - IBM Data Management Magazine - IIUG user view: Big data, big time ( Series data, warehouse acceleration, and 4GLs )... Read
16 May 11 - Business Wire - HiT Software Announces DBMoto for Enterprise Integration, Adds Informix. Log-based Change Data Capture... Read
21 Mar 11 - Yahoo! Finance - IBM and Cable&Wireless Worldwide Announce UK Smart Energy Cloud... Read
14 Mar 11 - MarketWatch - Fuzzy Logix and IBM Unveil In-Database Analytics for IBM Informix... Read
11 Mar 11 - InvestorPlace - It's Time to Give IBM Props: How many tech stocks are up 53% since the dot-com boom?... Read
9 Mar 11 - DBTA - Database Administration and the Goal of Diminishing Downtime... Read
2 Feb 11 - DBTAs - Informix 11.7 Flexible Grid Provides a Different Way of Looking at Database Servers... Read
27 Jan 11 - exactsolutions - Exact to Add Informix Support to Database Replay, SQL Monitoring Solutions... Read
25 Jan 11 - PR Newswire - Bank of China in the UK Works With IBM to Become a Smarter, Greener Bank... Read
12 Oct 10 - Database Trends and Applications - Informix 11.7: The Beginning of the Next Decade of IBM Informix... Read
20 Sep 10 - planetIDS.com - ITG analyst paper: Cost/Benefit case for IBM Informix as compared to Microsoft SQL Server... Read
20 Jul 10 - IBM Announcements - IBM Informix Choice Edition V11.50 helps deploy low-cost scalable and reliable solutions for Apple Macintosh and Microsoft Windows... Read
20 Jul 10 - IBM Announcements - Software withdrawal: Elite Support for Informix Ultimate-C Edition... Read
24 May 10 - eWeek Europe - IBM Supplies Database Tech For EU Smart Grid... Read
23 May 10 - SiliconIndia - IBM's smart metering system allows wise use of energy... Read
21 May 10 - CNET - IBM to help people monitor energy use... Read
20 May 10 - ebiz - IBM Teams With Hildebrand To Bring Smart Metering To Homes Across Britain... Read
19 May 10 - The New Blog Times - Misurare il consumo energetico: DEHEMS è pronto... Read
19 May 10 - ZDNet - IBM software in your home? Pact enables five-city smart meter pilot in Europe... Read
17 March 10 - ZDNet (blog) David Morgenstern - TCO: New research finds Macs in the enterprise easier, cheaper to manage than... Read
17 March 2010 - Virtualization Review - ...key components of Big Blue's platform to the commercial cloud such as its WebSphere suite of application ser vers and its DB2 and Informix databases... Read
10 February 2010 - The Wall Street Journal - International Business Machines is expanding an initiative to win over students and professors on its products. How do they lure the college crowd?... Read


End of Support Dates

IIUG on Facebook IIUG on Twitter

[ View Thread ] [ Post Response ] [ Return to Index ] [ Read Prev Msg ] [ Read Next Msg ]

IDS Forum

Re: deccmp return value differs between 2 informix

Posted By: Jonathan Leffler
Date: Wednesday, 22 July 2009, at 7:56 p.m.

In Response To: Re: deccmp return value differs between 2 informix (LAKSHMI DEVI PALANISSAMY)

On Wed, Jul 22, 2009 at 03:26, LAKSHMI DEVI
PALANISSAMY<lakshmidevip@hcl.in> wrote:
> I have referred the ESQL/C manual and understood the decimal strucure and the
> way it stores the exponent and base parts.

Congratulations. If you've understood it properly, you have done
well. It is not trivial.

> Yet I have another query. I am trying to create a table with a variable of
> SMALLFLOAT data type. The variable is having 3 decimal digits. When I tried to
> view the value using "dbaccess" command, more decimal digits are visible.

SMALLFLOAT is a very different type from DECIMAL. SMALLFLOAT
corresponds to a C float.

You say the variable has 3 decimal digits - all well and good, but C
float cannot represent most 3-digit decimal values exactly because it
is a binary floating point system, not a decimal floating point
system.

When the value that is the closest available approximation to your
proposed 3-digit C float value is printed with 8 or 9 digits of
precision (instead of the more conventional 6 or 7 digits of
precision), then you get weird fractional bits attached to what
appeared to be a nice round number.

One way of looking at the problem is: when the string representation
of the number is manipulated, is it the case that every decimal digit
in the string corresponds to some changes in the bits of the float
(but some bit patterns of the float cannot be represented by any
decimal string), or is it the case that every bit pattern can be
represented by at least one string of decimal digits, but some sets of
strings correspond to the same bit pattern.

The conventional way of looking at things is that the decimal
representation is more important, and it doesn't matter if some bit
patterns can't be represented. This view uses 7 digits maximum in the
decimal representation.

The alternative view is that the strings should be convertible such
that every bit pattern can be represented by one or more strings.
This view sometimes needs 8 or 9 decimal digits in the string to make
the necessary distinctions.

You can't have both views active at once because binary cannot
represent every decimal value exactly (because 5 is a factor of 10,
but is not a factor of 2).

> ====================================================
> I have written a stub as follows:
> #include <stdio.h>
> #include <string.h>
> #include <stdlib.h>
> EXEC SQL include decimal;
>
> main()
> {
>
> float a=0.120, b=0.005, c=1.804, d=0.300;
>
> EXEC SQL BEGIN DECLARE SECTION;
> float min1, min2, min3, min4;
> EXEC SQL END DECLARE SECTION;
>
> EXEC SQL connect to 'oas';
> EXEC SQL begin work;
>
> EXEC SQL drop table min_max;
>
> EXEC SQL create table min_max(dkey integer, min_value smallfloat);
>
> EXEC SQL insert into min_max values ('1', 0.120);
> EXEC SQL insert into min_max values ('2', 0.005);
> EXEC SQL insert into min_max values ('3', 1.804);
> EXEC SQL insert into min_max values ('4', 0.300);

You really don't need the quotes around the integers; fortunately for
you, Informix converts strings into integers rather readily, but not
all DBMS are as tolerant.

> EXEC SQL commit work;
>
> EXEC SQL select min_value into :min1 from min_max where dkey=1;
> printf ("Value1 is %f\n", min1);

This uses the built-in printf() interpretation of how to print the
data - it uses the 7 digit maximum formatting. Unlike DB-Access,
which uses the longer 8-9 digit notation.

You should try:

printf ("Value1 is %.3f\n", min1);
printf ("Value1 is %.4f\n", min1);
printf ("Value1 is %.5f\n", min1);
printf ("Value1 is %.6f\n", min1);
printf ("Value1 is %.7f\n", min1);
printf ("Value1 is %.8f\n", min1);
printf ("Value1 is %.9f\n", min1);

Eventually, you should see the values that DB-Access produces (with 8 or 9).

> EXEC SQL select min_value into :min2 from min_max where dkey=2;
> printf ("Value2 is %f\n", min2);
>
> EXEC SQL select min_value into :min3 from min_max where dkey=3;
> printf ("Value3 is %f\n", min3);
>
> EXEC SQL select min_value into :min4 from min_max where dkey=4;
> printf ("Value4 is %f\n", min4);
>
> printf ("Float values assigned are %f %f %f %f\n", a, b, c, d);
>
> EXEC SQL disconnect current;
> exit(0);
> }
> ============================================================
> Output of the query "select * from min_max":
>
> dkey min_value
>
> 1 0.119999997
>
> 2 0.00499999989
>
> 3 1.804000020000
>
> 4 0.300000012
> ============================================================
> Stub Output:
> Value1 is 0.120000
> Value2 is 0.005000
> Value3 is 1.804000
> Value4 is 0.300000
> Float values assigned are 0.120000 0.005000 1.804000 0.300000
> ============================================================
> When I retrieved the data from the database and tried to print the value, the
> correct values are displayed.
> But the table show the data with more precision (more than 9)?
> Can I ignore this difference?

For your sanity's sake, you should ignore the difference - or not use DB-Access.

Blatant plug:

SQLCMD does not try to print C float or double values with extraneous
decimal digits and it leads to saner outputs.

--
Jonathan Leffler #include <disclaimer.h>
Email: jleffler@earthlink.net, jleffler@us.ibm.com
Guardian of DBD::Informix v2008.0513 -- http://dbi.perl.org/
"Blessed are we who can laugh at ourselves, for we shall never cease
to be amused."
NB: Please do not use this email for correspondence.
I don't necessarily read it every week, even.
Marie von Ebner-Eschenbach - "Even a stopped clock is right twice a
day." - http://www.brainyquote.com/quotes/authors/m/marie_von_ebnereschenbac.html

Messages In This Thread

[ View Thread ] [ Post Response ] [ Return to Index ] [ Read Prev Msg ] [ Read Next Msg ]

IDS Forum is maintained by Administrator with WebBBS 5.12.