BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Best practices for datbase connection?          BorlandTalk.com Forum Index -> comp.lang.pascal.delphi.databases View previous topic :: View next topic   Author Message Guest Posted: Wed Oct 18, 2006 4:47 pm    Post subject: Best practices for datbase connection? Hi, I am currently writing an application in Delphi 5 which is supposed to connect to and diagnose Access databases using BDE. Since I am an inexperienced Delphi programmer I was hoping that you could help me out by sharing your best practices with me concerning database interaction. Where to put database connection? My initial thought is to put the database connection in the main form. Creating and opening it in the constructor, destroying and closing in the destructor. Where to put DataSources? Since many DataAware controls can connect to the same DataSource it seems to me that it belongs in a DataModule? How many DataModules? Should I use one big DataModule for all Querys and DataSources or should I have one DataModule for each pair of them or maybe something in between? How to connect Querys to database? As I have understood this is just a matter of using the same database name for the connection as well as the Queries? How to change database on the fly? Just change the alias for the connection? A lot of questions, hope you can bare with me. I have little time, no expertise around and want to get it right and write good code. Back to top Dan Guest Posted: Wed Oct 18, 2006 7:54 pm    Post subject: Re: Best practices for datbase connection? On 18 Oct 2006 04:47:26 -0700, MorrganMail (AT) gmail (DOT) com wrote: Quote: Hi, I am currently writing an application in Delphi 5 which is supposed to connect to and diagnose Access databases using BDE. Since I am an inexperienced Delphi programmer I was hoping that you could help me out by sharing your best practices with me concerning database interaction. Where to put database connection? My initial thought is to put the database connection in the main form. Creating and opening it in the constructor, destroying and closing in the destructor. Put them in a DataModule Quote: Where to put DataSources? Put them in the same DM Quote: Since many DataAware controls can connect to the same DataSource it seems to me that it belongs in a DataModule? Yes Quote: How many DataModules? Should I use one big DataModule for all Querys and DataSources or should I have one DataModule for each pair of them or maybe something in between? As many as you need I like to keep the total number of lines in the unit below a few hundred, so it is easier to find things. The form can have quite a few objects on it, such as queries, data sources, etc. as long as there isn't much code associated with them. It makes no difference in the final executable size or the processing speed. Make it easy on yourself. Quote: How to connect Querys to database? As I have understood this is just a matter of using the same database name for the connection as well as the Queries? Yes. Using the BDE to connect, which is probably what you will start with, drop a TDatabase object on your dm, give it a meaningful name, say dbMain. Then drop a TQuery object on the dm. Click the DatabaseName property in the object inspector, and you should se dbMain listed. Select it. Quote: How to change database on the fly? Just change the alias for the connection? Look up TDatabase.DatabaseName in the Help for details. This is a bit complicated at first. I recommend using an alias for the database; it makes program development easier because it separates the connection details from your app. Aliases are set and managed with the BDEadministrator program which is included in your Delphi software. If you know in advance what the different DBs are that the user will connect to, you can use a different alias for each one, and the user can select the desired one from a list. Your code would then change the Alias property in the TDatabase object at runtime (while the connection is closed). Quote: A lot of questions, hope you can bare with me. I have little time, no expertise around and want to get it right and write good code. 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