BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Null fields not printing correctly          BorlandTalk.com Forum Index -> Delphi Databases (ADO) View previous topic :: View next topic   Author Message Andrew Skinner Guest Posted: Tue Feb 08, 2005 9:57 am    Post subject: Null fields not printing correctly I've got (D7, Jet OLE/ADO, Access 97 tables) an application which works correctly (big news in itself). In order to print out some small tables I'm copying to a richedit with code like this (don't really want the trouble of a report writer, though it would be prettier, version 2 perhaps?): dataset.first while not dataset.eof do begin temp := #0; temp := temp + datasetFIRSTFIELD.value + #32; temp := temp + datasetNEXTFIELD.value; richedit.lines.add(temp); dataset.next; {temp and the fields are strings of course} end; This works spot on if nextfield isn't null. If it is null the last non-null value of nextfield is added, until another non null nextfield is encountered. I've worked around it by putting #32 in null fields, and since the whole thing is small this is no big deal. I assume this is a feature not a bug, with some complex big database reason for it, which I shall never understand, but intelligent comments are welcome. Andrew Back to top Mike Shkolnik Guest Posted: Tue Feb 08, 2005 11:53 am    Post subject: Re: Null fields not printing correctly Use the datasetFIRSTFIELD.AsString instead datasetFIRSTFIELD.value -- With best regards, Mike Shkolnik EMail: [email]mshkolnik (AT) scalabium (DOT) com[/email] http://www.scalabium.com "Andrew Skinner" <skinnner (AT) getridofthisbit (DOT) summerfld.demon.co.uk> wrote in message news:42088d16 (AT) newsgroups (DOT) borland.com... Quote: I've got (D7, Jet OLE/ADO, Access 97 tables) an application which works correctly (big news in itself). In order to print out some small tables I'm copying to a richedit with code like this (don't really want the trouble of a report writer, though it would be prettier, version 2 perhaps?): dataset.first while not dataset.eof do begin temp := #0; temp := temp + datasetFIRSTFIELD.value + #32; temp := temp + datasetNEXTFIELD.value; richedit.lines.add(temp); dataset.next; {temp and the fields are strings of course} end; This works spot on if nextfield isn't null. If it is null the last non-null value of nextfield is added, until another non null nextfield is encountered. I've worked around it by putting #32 in null fields, and since the whole thing is small this is no big deal. I assume this is a feature not a bug, with some complex big database reason for it, which I shall never understand, but intelligent comments are welcome. Andrew Back to top Andrew Skinner Guest Posted: Tue Feb 08, 2005 12:16 pm    Post subject: Re: Null fields not printing correctly Thank you, but why? It still seems anomalous behviour. Andrew Back to top Patrick Guest Posted: Tue Feb 08, 2005 1:37 pm    Post subject: Re: Null fields not printing correctly Quote: Thank you, but why? Because AsString returns a String, which will be '' if the underlying value is null, and the value as a string if not? Because it has the behavior you want? Quote: It still seems anomalous behviour. Expecting datasetNEXTFIELD.value to have a value when it is null seems anomalous. Time for my coffee. Back to top Andrew Skinner Guest Posted: Tue Feb 08, 2005 8:17 pm    Post subject: Re: Null fields not printing correctly The anomaly is that the value of the previous row is carried forward as if it were in the new row. Anyone can do puns on "as string" and "value", the explanation of why is what interested me. Andrew Back to top Patrick Guest Posted: Tue Feb 08, 2005 8:44 pm    Post subject: Re: Null fields not printing correctly Quote: The anomaly is that the value of the previous row is carried forward as if it were in the new row. Got it. I agree, that is odd--I for sure don't know if it is a bug or by design. Quote: Anyone can do puns on "as string" and "value", the explanation of why is what interested me. I guess I mistook what your goal was; certainly replacing .Value with ..AsString is a better 'work around' than filling null fields with a space, as it does not change your data. Back to top Andrew Skinner Guest Posted: Tue Feb 08, 2005 8:47 pm    Post subject: Re: Null fields not printing correctly I will, of course, rewrite with .asstring, though the work around works well enough in the four tables with up to a dozen records each. Andrew Back to top Viatcheslav V. Vassiliev Guest Posted: Tue Feb 08, 2005 10:03 pm    Post subject: Re: Null fields not printing correctly If I remebmer correctly, change function TWideStringField.GetAsWideString: WideString; begin GetData(@Result, False); end; to function TWideStringField.GetAsWideString: WideString; begin Result := ''; GetData(@Result, False); end; This code is in DB unit. It seems that Delphi compiler does not always initialize (or Finalize) Result if it is WideString in function prolog. or if not GetData(@Result, False) then Result := ''; //------------------------------------------ Regards, Vassiliev V. V. http://www.managed-vcl.com - using .Net objects in Delphi for Win32 + ADO.Net http://www.oledbdirect.com - The fastest way to access MS SQL Server, MS Jet (Access) and Interbase (through OLEDB) "Andrew Skinner" <skinnner (AT) getridofthisbit (DOT) summerfld.demon.co.uk> ÓÏÏÂÝÉÌ/ÓÏÏÂÝÉÌÁ × ÎÏ×ÏÓÔÑÈ ÓÌÅÄÕÀÝÅÅ: news:42088d16 (AT) newsgroups (DOT) borland.com... Quote: I've got (D7, Jet OLE/ADO, Access 97 tables) an application which works correctly (big news in itself). In order to print out some small tables I'm copying to a richedit with code like this (don't really want the trouble of a report writer, though it would be prettier, version 2 perhaps?): dataset.first while not dataset.eof do begin temp := #0; temp := temp + datasetFIRSTFIELD.value + #32; temp := temp + datasetNEXTFIELD.value; richedit.lines.add(temp); dataset.next; {temp and the fields are strings of course} end; This works spot on if nextfield isn't null. If it is null the last non-null value of nextfield is added, until another non null nextfield is encountered. I've worked around it by putting #32 in null fields, and since the whole thing is small this is no big deal. I assume this is a feature not a bug, with some complex big database reason for it, which I shall never understand, but intelligent comments are welcome. Andrew Back to top Del M Guest Posted: Tue Feb 08, 2005 10:08 pm    Post subject: Re: Null fields not printing correctly Andrew, This is really esoteric but ... if you use the .value method, no recasting of the data is done. Since null is unknown type, you cant concatenate it with any other type (#32 included), so that is why you need to have "asstring". Remeber Delphi is a "strictly typed" language, unlike VB which is more like a kitchen appliance not a real programming language. Null is not empty, blank, space, vapordata or the like, it is "unknown type/value/neverbeenanything" Back to top John Herbster Guest Posted: Tue Feb 08, 2005 11:32 pm    Post subject: Re: Null fields not printing correctly "Andrew Skinner" wrote Quote: ... on "as string" and "value", the explanation of why is what interested me. Andrew, Do you have the source code defining the AsString and Value available? If so, I suggest studying it. Regards, JohnH Back to top Andrew Skinner Guest Posted: Fri Feb 11, 2005 9:44 am    Post subject: Re: Null fields not printing correctly Thanks to everyone. Asstring makes it work. Quote: This is really esoteric but ... if you use the .value method, no recasting of the data is done. Since null is unknown type, you cant concatenate it with any other type (#32 included), so that is why you need to have "asstring". Remeber Delphi is a "strictly typed" language, unlike VB which is more like a kitchen appliance not a real programming language. Null is not empty, blank, space, vapordata or the like, it is "unknown type/value/neverbeenanything" I can sort of see what you are driving at, but the problem was not that the concatenation failed, but that if the field was null the value in the prior row was used rather than being discarded. I can almost see what you are saying, and thanks, I think I follow it. Anyhow, it works, and I'll stop the lazy use of .value, since usually it isn't needed, one can use the real type. Are not variants at variance with a strongly typed language? They were a fairly late addition to Object Pascal were they not? <G> Andrew Back to top Del M Guest Posted: Sat Feb 12, 2005 1:03 pm    Post subject: Re: Null fields not printing correctly Yes, variants are not strongly typed. I think they were put there for VB programmers who were trying to learn to use a "real" programming language <g> Back to top Bill Todd Guest Posted: Sat Feb 12, 2005 3:09 pm    Post subject: Re: Null fields not printing correctly More likely because they are used extensively in COM. :) -- Bill Todd (TeamB) TeamB cannot answer questions received via email Del M wrote: Quote: I think they were put there for VB programmers who were trying to learn to use a "real" programming language g Back to top Del M Guest Posted: Sat Feb 12, 2005 7:11 pm    Post subject: Re: Null fields not printing correctly I know, but I cant pass up a chance to snipe at VB .. and of course we all know were COM was invented.. :-) Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         BorlandTalk.com Forum Index -> Delphi Databases (ADO) All times are GMT Page 1 of 1   Jump to: Select a forum C++ Builder Newsgroups----------------C++ BuilderC++ Builder (ActiveX)C++ Builder (Announcements)C++ Builder (Command Line Tools)C++ Builder DatabasesC++ Builder Databases (ADO)C++ Builder Databases (Desktop)C++ Builder Databases (InterBase Express)C++ Builder Databases (Multi-Tier)C++ Builder Databases (SQL Servers)C++ Builder (Graphics)C++ Builder (IDE)C++ Builder (Internet)C++ Builder (Internet Socket)C++ Builder (Internet Web)C++ Builder (Jobs)C++ Builder (Language)C++ Builder (Language C++)C++ Builder (Compatibility with MFC)C++ Builder (Native API)C++ Builder (Non-Technical)C++ Builder (Students)C++ Builder (Third Party Tools)C++ Builder (Upgrade)C++ Builder (VCL)C++ Builder (VCL Components Usage)C++ Builder (VCL Components Development)C++ Builder (VCL Usage)C++ Builder (WinAPI)C++ Builder Installation Delphi Newsgroups----------------Delphi (General)Delphi ActiveX Controls UsageDelphi ActiveX Controls DevelopmentDelphi As400Delphi DatabasesDelphi Databases (ADO)Delphi Databases (dbExpress)Delphi Databases (Desktop)Delphi Databases (InterBase Express)Delphi Databases (Multi-Tier)Delphi Databases (SQL Servers)Delphi DeploymentDelphi GraphicsDelphi IDEDelphi InternationalizationDelphi InternetDelphi Internet Isapi-WebBrokerDelphi Internet WebSnapDelphi Internet WinsockDelphi JobsDelphi Language BASMDelphi Language ObjectPascalDelphi Model Driven Architecture (General)Delphi Model Driven Architecture (Third Party)Delphi MultimediaDelphi Native APIDelphi Non-TechnicalDelphi ObjectPascalDelphi OLE AutomationDelphi OO designDelphi OpenToolsAPIDelphi Reporting-ChartingDelphi RTLDelphi StudentsDelphi TeamSourceDelphi Thirdparty ToolsDelphi Thirdparty Tools (General)Delphi Thirdparty Tools (IntraWeb)Delphi Thirdparty Tools (RaveReports)Delphi UpgradeDelphi VCLDelphi VCL ComponentsDelphi VCL Components UsingDelphi VCL Components WritingDelphi WebServices SOAPDelphi WinAPIDelphi XMLDelphi Installationcomp.lang.pascal.delphi.components.misccomp.lang.pascal.delphi.components.usagecomp.lang.pascal.delphi.components.writingcomp.lang.pascal.delphi.databasescomp.lang.pascal.delphi.misccomp.sources.delphi JBuilder Newsgroups----------------JBuilderJBuilder AnnouncementsJBuilder Applet IssuesJBuilder As400JBuilder CompilerJBuilder CORBA/RMIJBuilder DatabasesJBuilder DB SwingJBuilder DebuggerJBuilder DeploymentJBuilder DocumentationJBuilder EnterpriseJBuilder HandheldJBuilder IDEJBuilder JavaJBuilder JavaAPIJBuilder Java LanguageJBuilder Java SwingJBuilder Java BeansJBuilder Java Beans UsageJBuilder Java Beans DevelopmentJBuilder JBCLJBuilder JDataStoreJBuilder JobsJBuilder LinuxJBuilder MacintoshJBuilder & MobileSetJBuilder MultiLingual AppsJBuilder Non-TechnicalJBuilder OpenToolsJBuilder Servlets (JSP)JBuilder StudentsJBuilder Team DevelopmentJBuilder Thirdparty ToolsJBuilder UpgradeJBuilder Installation InterBase Newsgroups----------------InterBaseInterBase Bug DiscussionInterBase GeneralInterBase IBConsoleInterBase OpenSourceInterBase ReplicationInterBase SQLInterBase ThirdpartyInterBase Installation Miscellaneous Borland Newsgroups----------------AppCenterAppServerEnteraVisiBroker  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.