1. EDB Question
I'm starting to code writing some data to my Database and I have a couple of
generic questions on the EDB commands:
1.) What exactly is returned when you do a db_create or db_open, at various
points it states that DB_OK is returned or 0 is returned. Is DB_OK a variable
that equals 0? Just wondering for my own education.
2.) If my database file exists or has to be created, I'm assuming we have to
give the file path. So:
db_create("c:\\somedir\\somesubdir\\myfile.edb")
Is this correct?
3.) Now, after creating/opening the EDB, we have to select it. Do we need to
give the total pathname, or can we just give the file name, and do we need the
.edb extension? i.e.
db_select("c:\\somedir\\somesubdir\\myfile.edb")
or is it:
db_select("myfile")
I'm sorry if this has been gone over before...if it has, just point me to where
and I'll stop bothering you guys!!! But the manual is rather vague...
Thanks!
Rich
2. Re: EDB Question
Rich Klender wrote:
>
> I'm starting to code writing some data to my Database and I have a couple of
> generic questions on the EDB commands:
> 1.) What exactly is returned when you do a db_create or db_open, at various
> points it states that DB_OK is returned or 0 is returned. Is DB_OK a variable
> that equals 0? Just wondering for my own education.
If you look at the docs for EDB the db_create() function returns an integer.
Also, DB_OK is a constant defined in database.e with a value of 0.
So your create would look something like:
atom rtn_code
rtn_code = db_create("Myfile.edb",DB_LOCK_NO)
if rtn_code = DB_OK then
do something here
end if
Or like
if db_create("Myfile.edb", DB_LOCK_NO) = DB_OK then
do something here
end if
Either way works.
>
> 2.) If my database file exists or has to be created, I'm assuming we have to
> give the file path. So:
>
> db_create("c:\\somedir\\somesubdir\\myfile.edb")
>
> Is this correct?
Yes. BUT I would advise against hard-coding path names. You could use
current_dir() to get the current directory if you wanted to include the path in
the db_create(). For example:
sequence path
path = current_dir()
if db_create(path & "\\myfile.edb", DB_LOCK_NO) = DB_OK then
do something here
end if
or just assume you're current directory is correct:
if db_crate("myfile.edb",DB_LOCK_NO) = DB_OK then
do something here
end if
However this doesn't always work as you can't assume a current or working
directory has been set. If you want to ensure that the file is created in the
same directory as the program you could use the command_line() function and
extract the program's path from the returned value. Then use the path in the
db_create() function.
>
> 3.) Now, after creating/opening the EDB, we have to select it. Do we need to
> give the total pathname, or can we just give the file name, and do we need the
> .edb extension? i.e.
>
> db_select("c:\\somedir\\somesubdir\\myfile.edb")
>
> or is it:
>
> db_select("myfile")
>
Again, the answer to your path question is probably the same as my previous
answer. I've never tried to use db_select() without the extensions so I'm not
sure what it would do. I always like to specify extensions but that's just me.
> I'm sorry if this has been gone over before...if it has, just point me to
> where
> and I'll stop bothering you guys!!! But the manual is rather vague...
>
Hey, no problem! Someone answered these questions for me 7 years ago so it's
only fair!
Jonas Temple
http://www.yhti.net/~jktemple
3. Re: EDB Question
- Posted by "Greg Haberek" <ghaberek at gmail.com>
Feb 02, 2007
-
Last edited Feb 03, 2007
On 2/2/07, Rich Klender <guest at rapideuphoria.com> wrote:
>
> I'm sorry if this has been gone over before...if it has, just point me to
> where
> and I'll stop bothering you guys!!! But the manual is rather vague...
Here is some generic code that I use as the base of all my database stuffs:
(I wrote this out in GMail so don't sue me if its broken.)
global function db_load( sequence path, integer lock )
integer ret
-- try selecting the database
ret = db_select( path )
if ret = DB_OK then
-- success!
return ret
end if
-- select failed, try open
ret = db_open( path, lock )
if ret = DB_OK then
-- success!
return ret
end if
-- open failed, try create
ret = db_create( path, lock )
if ret = DB_OK then
-- success!
return ret
end if
-- failure.
return ret
end function
global function db_load_table( sequence table )
integer ret
-- try selecting the table
ret = db_select_table( table )
if ret = DB_OK then
-- success!
return ret
end if
-- select failed, try create
ret = db_create_table( table )
if ret = DB_OK then
-- success!
return ret
end if
-- failure.
return ret
end function
Keep in mind that when you create/open/select a database it is the
active database until you create/open/select another. So if you call
db_create(), that database is the current database, there is no need
to call db_select() right after that, its redundant. The same rule
goes for tables, except that when you first create/open/select a
database, no table is selected.
~Greg
4. EDB Question
Hi,
Does db_close() close all EDB's that are open or just the current EDB.
Thanks Tony
Come visit me at www.locksdownunder.com
5. Re: EDB Question
Hi, Tony,
The EDS docs state:
Comments Call this procedure when you are finished with the current
database.
Also note that db_open() and db_create() both make the database just
opened or created the current database.
So, it would seem that when you db_close() the current database,
then the database opened (or created) previous to that one becomes
the current database. However, that results in an error. The db_select() in the
last
if statement is required, else it seems that no open database is current.
(Probably, only Rob can verify that). But once selected(), the EDB will require
its
own db_close().
Hope this helps.
The following example worked for me:
with trace
sequence s
trace(1)
if db_open("PATTHIST", DB_LOCK_EXCLUSIVE) != DB_OK then
puts(1, "Could not open database PATTHIST.EDB. Aborting ...\n")
abort(1)
end if
if db_open("COMMDATA", DB_LOCK_EXCLUSIVE) != DB_OK then
puts(1, "Could not open database COMMDATA.EDB. Aborting ...\n")
abort(1)
end if
s = db_table_list() -- just to verify what EDB you've got here
db_close()
if db_select("PATTHIST") != DB_OK then
puts(1,"PATTHIST.EDB could not be selected. Abort.")
abort(1)
end if
s = db_table_list() -- just to verify what EDB you've got here
db_close()
Regards,
Jim
Tony Steward wrote:
>
> Hi,
> Does db_close() close all EDB's that are open or just the current EDB.
>
> Thanks Tony
>
> Come visit me at www.locksdownunder.com
>
