BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  How to get table fields          BorlandTalk.com Forum Index -> Delphi Databases (SQL Servers) View previous topic :: View next topic   Author Message Marcelo Guest Posted: Tue May 25, 2004 4:57 pm    Post subject: How to get table fields Hi! I wanna get the fields of an unknown table. I use a TQuery and a "select * from table" to open the table and then iterate trought the field list. I access the table with a clientdataset and a remote provider. The fact is that when I open a big table all the registers are sent to the client and this takes a long time. How can I open a table without returning any result set? something like "select * from table where false. Greetings, Marcelo. Back to top Del Murray Guest Posted: Tue May 25, 2004 5:04 pm    Post subject: Re: How to get table fields It depends on the database of course, which you didn't tell us anything about :-( you can do 'select * from sometable where 1=2' and you will get a tquery that knows all about the columns of the table but has no rows Back to top alex Guest Posted: Tue May 25, 2004 5:12 pm    Post subject: Re: How to get table fields Set ClientDataSet.PacketRecords property to 0 before Open and after Open you will receive only field descriptions. Don't forget to set PacketRecords to non zero when you will need data. However there are hidden problem in using this way. PacketRecords := 0 means that TQuery will be opened on appserver and no records will be sent from appserver to client. But TQuery's realization is such that it will fetch one record from database. This is not a problem if your statement is 'select * from <some table>'. But it is a big problem when your statement is complex (has group by, order and etc.) because in some cases (when table is huge or other) database server has to do very much work to retrieve this (unnecessary for you) first record. P.S. But in exactly your case this method is a solution :) "Marcelo" <mmartinez (AT) csg-consulting (DOT) com.ar> wrote Quote: Hi! I wanna get the fields of an unknown table. I use a TQuery and a "select * from table" to open the table and then iterate trought the field list. I access the table with a clientdataset and a remote provider. The fact is that when I open a big table all the registers are sent to the client and this takes a long time. How can I open a table without returning any result set? something like "select * from table where false. Greetings, Marcelo. Back to top Marcelo Guest Posted: Tue May 25, 2004 5:39 pm    Post subject: Re: How to get table fields Hi! Im using SQL Server trought midas 6, but Im trying to implement a DBinf component for a Korzh Simple Query component and should work with any remote ODBC database, so do you think that "where 1=2" should work with any database? Thanks in advance, Marcelo. "Del Murray" <Del.Murray (AT) N_S_CreditHawk (DOT) Net> escribió en el mensaje news:40b37bd8$1 (AT) newsgroups (DOT) borland.com... Quote: It depends on the database of course, which you didn't tell us anything about :-( you can do 'select * from sometable where 1=2' and you will get a tquery that knows all about the columns of the table but has no rows Back to top Marcelo Guest Posted: Tue May 25, 2004 5:47 pm    Post subject: Re: How to get table fields Thank you for your quick answer! Im trying it right now I seems to work fine. Thanks, Marcelo. "alex" <no (AT) no (DOT) com> escribió en el mensaje news:40b37e6a (AT) newsgroups (DOT) borland.com... Quote: Set ClientDataSet.PacketRecords property to 0 before Open and after Open you will receive only field descriptions. Don't forget to set PacketRecords to non zero when you will need data. However there are hidden problem in using this way. PacketRecords := 0 means that TQuery will be opened on appserver and no records will be sent from appserver to client. But TQuery's realization is such that it will fetch one record from database. This is not a problem if your statement is 'select * from <some table>'. But it is a big problem when your statement is complex (has group by, order and etc.) because in some cases (when table is huge or other) database server has to do very much work to retrieve this (unnecessary for you) first record. P.S. But in exactly your case this method is a solution :) "Marcelo" <mmartinez (AT) csg-consulting (DOT) com.ar> wrote in message news:40b37a98 (AT) newsgroups (DOT) borland.com... Hi! I wanna get the fields of an unknown table. I use a TQuery and a "select * from table" to open the table and then iterate trought the field list. I access the table with a clientdataset and a remote provider. The fact is that when I open a big table all the registers are sent to the client and this takes a long time. How can I open a table without returning any result set? something like "select * from table where false. Greetings, Marcelo. Back to top Edwin Walker Guest Posted: Thu May 27, 2004 3:09 pm    Post subject: Re: How to get table fields I never tried where 1=2, but I do where ID=-1 and I know that works. Edwin "Marcelo" <mmartinez (AT) csg-consulting (DOT) com.ar> wrote Quote: Hi! Im using SQL Server trought midas 6, but Im trying to implement a DBinf component for a Korzh Simple Query component and should work with any remote ODBC database, so do you think that "where 1=2" should work with any database? Thanks in advance, Marcelo. "Del Murray" <Del.Murray (AT) N_S_CreditHawk (DOT) Net> escribió en el mensaje news:40b37bd8$1 (AT) newsgroups (DOT) borland.com... It depends on the database of course, which you didn't tell us anything about :-( you can do 'select * from sometable where 1=2' and you will get a tquery that knows all about the columns of the table but has no rows Back to top Geert Gruwez Guest Posted: Wed Jun 09, 2004 6:34 am    Post subject: Re: How to get table fields The ID=-1 will only work if the table has a column with a field ID 1=2 will always work on the other hand ! Geert "Edwin Walker" <enwalker (AT) ameritech (DOT) net> schreef in bericht news:40b60406$1 (AT) newsgroups (DOT) borland.com... Quote: I never tried where 1=2, but I do where ID=-1 and I know that works. Edwin "Marcelo" <mmartinez (AT) csg-consulting (DOT) com.ar> wrote in message news:40b38497 (AT) newsgroups (DOT) borland.com... Hi! Im using SQL Server trought midas 6, but Im trying to implement a DBinf component for a Korzh Simple Query component and should work with any remote ODBC database, so do you think that "where 1=2" should work with any database? Thanks in advance, Marcelo. "Del Murray" <Del.Murray (AT) N_S_CreditHawk (DOT) Net> escribió en el mensaje news:40b37bd8$1 (AT) newsgroups (DOT) borland.com... It depends on the database of course, which you didn't tell us anything about :-( you can do 'select * from sometable where 1=2' and you will get a tquery that knows all about the columns of the table but has no rows 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 (SQL Servers) 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.