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| InterBase
Express FAQ |
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| Where can I
download latest version of IBX? Always from CodeCentral.
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| How does Refresh work in IBX? Contrary to BDE's
behavior, the Refresh method in IBX refreshes
only the current record (where the dataset cursor
is positionated) in order to minimize network traffic. If you
want to refresh more than one record, close and re-open the
dataset.
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How
does RecordCount work in IBX?
Recordcount
returns the number of fetched records. Because
IBX only fetches new records when something
actually asks for the next record, after opening
a dataset RecordCount will return 0 if the
dataset is empty and 1 if it is not. After a
FetchAll (not an advisable practice), RecordCount
will return the total number of records in the
dataset.
In
IBX, RecordCount should never be used to rely on
how many records exist since it is only reliable
for Paradox and DBase. If you really need to know
the number of records in a dataset, issuing a
"SELECT COUNT(*)" in a separate TIBSQL does the trick in most cases without
the overhead of a FetchAll.
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When
connecting a DBLookUpComboBox to a TIBQuery, I
see just one record in the drop down list. Why?
Again,
IBX only fetches records when something actually
asks for the next record. In the case of the
DBLookupCombo, it is incorrectly relying on the
RecordCount (see previous question) to scale the
drop down area before trying to fill the drop
down list.
To
solve it, just do the following in the combo's AfterOpen event (to force the fetching of at
least a handful of records; this will increase
the value of RecordCount):
With (Sender as TDataset) do begin
MoveBy(MyDBLookupCombo.DropDownCount);
First;
end; |
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| Why should I
avoid using TIBTable? Short
answer:
TIBTable is not C/S friendly, it is included in
IBX for compatibility reasons only. TIBDataSet is
the direct replacement.
Not-so-short
answer: The
Table Paradigm comes from file based databases like
Paradox. Basically no matter where the
table is located all the rows and all the columns
(and usually all the index information) is brought locally so the SQL
engine (like the BDE) can work
with the data. Since all the data must be
retrieved locally anyways the TTable
was designed to work better in that environment.
The C/S Paradigm says that you let the server do
the work of selecting what data
you need and you return only that which the user
needs. IOW you may only return
3 of the 5 columns or only 100 of the 1,000,000
rows etc. The Table paradigm
tends to flood the network and does not scale
well at all in the C/S world.
TIBDataset you just fill out the SelectSQL for
what data needs to be retrieved
and the right click on it and select the DataSet
Editor to let it help you
determine the InsertSQL, ModifySQL, DeleteSQL and
RefreshSQL. Once those are
filled out you have a fully updatable result set.
And it will be less expensive
in terms of speed, network traffic and memory
than a table based paradigm.
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| I can't see
updates made by other users. Why? First, check if your
transaction isolation mode is Read Committed. If
it's Snapshot (the Interbase default), you'll
always get a consistent view of the data -- i.e.,
you won't see changes made by other users. Hint: To change the
transaction isolation mode to Read Committed,
double-click on your TIBTransaction component.
Next, make sure
your application actually commits a transaction
after any updates, either by using
CommitRetaining or Commit.
Finally, if your
dataset is already open on your PC when another
user performs some updates, you will see those
changes only after you close and re-open the
dataset, or after you call the Refresh method and the
updated record is the current record you are viewing.
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| Why
do my datasets close when I call Commit or
Rollback?
Short answer:
That's
normal IBX behavior. Use CommitRetaining or RollbackRetaining
to keep your datasets open.
Not-so-short-answer:
In IBX, if you call Commit or
Rollback this brings to an end the existence
of a transaction handle on the client. As a
result, all things that depend upon that transaction need to be rectified or they will become invalid.
Without a transaction, InterBase doesn't know which versions of the
records you should see -- i.e., it doesn't know whether your
isolation mode should be ReadCommitted or Snapshot.
There are
essentially two things that depend on a
transaction. 1) Any changes that have been posted
to the server and 2) any currently open "cursors".
A cursor in
InterBase is what you get after executing a
select statement with multiple records to return.
You interact with the cursor by requesting
fetches until that cursor is exhausted. All open
cursors are dependant upon a transaction handle
being present and if that transaction is ended
the cursor will become invalid.
So, what IBX
does when you call Commit or Rollback is to close
all of your open datasets in order to avoid
getting an invalid cursor error. This is because
with IBX there isn't a layer that provides
isolation between having datasets opened and
ending transactions as the BDE and IBO do.
If you want to
keep your datasets open, it is recommended that
you use CommitRetaining or RollbackRetaining for
processing your logical units of work (changes)
to avoid datasets closing and that you reserve
the usage of Commit and Rollback for when you
want to free up the server so it can do its
garbage collection, etc. You should do a "hard"
Commit or Rollback as frequently as possible, though.
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| When
using Cached Updates with a Master/Detail relation, details
disappear when I post. What gives?
This behavior is up at the
TDataset level. When you go into Edit mode (or when
you ApplyUpdates) the DataLink is passed a message that the
cursor has been
repositioned. This message will cause detail queries to close
and re-open on the
"new" position. The only way to stop this is to
break the DataLink. Set the detail's DataSource to nil before applying
the master's update. |
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| InterBase FAQ |
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| Where can I
download latest InterBase release? Currently
there are two companies that provide InterBase Open Source releases,
namely Borland and IBPhoenix.
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| Is InterBase free or do I
have to buy any licenses? It depends on the
product and the company you select.
- InterBase,
from Borland
Borland is currently releasing two "flavors" of
InterBase.
The Open Source version
is absolutely free for commercial development and deployment,
but Borland does not provide support for it.
The Certified
version is a commercial product, it does require paid licenses
for the server and the clients but includes additional
features not found in the Open Sourced product, like the
replication engine, the ODBC driver, etc.
Borland has
posted a Response
to Recent Inquiries document, with questions and
answers regarding the differences between the two
InterBase versions.
- Firebird,
from IBPhoenix
Firebird is an Open Source project based on the original
InterBase source code released by Borland. Firebird is a now a
stable, free InterBase, as it does not require any licenses.
IBPhoenix
is the organization behind Firebird. IbPhoenix provides new
releases of Firebird and commercial support options for both
Firebird and InterBase.
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| What
is
the proper procedure for installing InterBase?
You'll find
the following install info sites useful:
For
Linux/Unix:
For Windows:
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| What
is the difference between InterBase Classic Server and Super
Server for Linux?
Read this
article from Borland. In addition to this, note that
Classic supports SMP, while SuperServer presently does not.
However, this will change in the not-so-distant
future.
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| How
do I set up InterBase to start automatically in Linux?
Classic Server:
Classic is usually invoked by inetd or xinetd automatically,
no need to do anything.
Super Server:
Use a script. At the InterBase2000.org
site you'll find the ibserver script I use. Once
the server is running, you can stop it with
"/etc/rc.d/init.d/ibserver stop" and restart it with
"/etc/rc.d/init.d/ibserver sart".
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| Where
do I get the documentation?
Get the InterBase
6.0 Documentation Set (10.04 mb, PDF) from the Interbase
Documentation page. Despite the "Beta" condition,
it is quite comprehensive and well worth downloading.
According to Borland, the final revision of the docs should be
released soon.
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| IBConsole
can't connect to my InterBase Classic Server in Linux.
Usually you get the following
error:
Cannot attach to services
manager.
Services functionality will be supported in a later version of
the product.
This is because the Services
API (used by IBConsole) is only supported in SuperServer
architecture. You can't use it with Classic
architecture. Try a different InterBase administration tool
from the Contributed
Downloads at IBPhoenix.
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| What
are the default user and password for InterBase?
Username = SYSDBA, Password =
masterkey. Change the (case-sensitive)
password
is the first thing to do after installation.
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| Is it possible to
use BDE with dialect 3 new features? If you're using SQL
Links, no. The current SQL Links driver for InterBase 6 does not support Dialect 3. You *can*
connect to a IB6 Dialect 1 database, though.
For now you
might use the BDE with an ODBC driver that knows
dialect 3, or wait for a new SQL Links driver,
which should be released at the same time as
Delphi 6.
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| Is there an ODBC driver
for InterBase 6? As a matter of fact,
there are several. Check out the list of interface
components from IBPhoenix and the Packages and Utilities
list
from Claudio Valderrama.
A popular choice
is the ODBC driver from EasySoft. It will be included
with the certified release of InterBase 6 from Borland.
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| Does InterBase support the LIMIT / TOP predicate in a Select? InterBase does not
support the non-ANSI Standard LIMIT / TOP syntax.
You can write a Stored Procedure that is
selectable and exits after the passed value of
iterations.
You'll have to
modify the following example slightly, but it
should get you on the right track:
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|
InterBase
does not have a native Boolean data type. How can I create one
myself?
- Declare
a field of type CHAR and use CHECK CONSTRAINTS to limit
the values that are allowed to be entered into it.
Example:
CHAR(1) CHECK (VALUE IN
("Y", "N")) NOT NULL;
- Similar to above but use a
domain to create a global data type for the database so
that you may reuse the data type more easily.
Example:
CREATE DOMAIN YESNO AS CHAR(1) CHECK
(VALUE IN ("Y","N")) NOT NULL;
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| How
do I start using User Defined Functions (UDF) in InterBase?
InterBase 6 comes with a
ready-to-use library of user defined functions. UDFs are
included in <Interbase>\UDF\ib_udf.dll
in the Windows version and in /opt/interbase/UDF/ib_udf
in Linux/Unix. This functions must be declared on all databases where you want to use them; declarations are included
in the ib_udf.sql script in both
versions.
Here's
what to do for Linux/Unix
systems:
- Change to the InterBase
bin directory:
cd /opt/interbase/bin
- Using the isql utility,
execute the ib_udf.sql script on your database:
./isql /path/to/yourdb/yourdb.gdb -i
/opt/interbase/examples/ib_udf.sql
For Windows
systems:
- Connect to
your database using IBConsole or your IB
administration tool.
- Execute the ib_udf.sql script
located in <InterBase>\examples\udf.
UDFs should now be ready to
use in yourdb.gdb database. If you plan to write your own
functions, refer to the following tutorial:
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| What
if my question isn't on this list?
Don't panic :-) You can
search millions of InterBase / IBX news post on this sites:
No luck yet? Post your
question to the forums listed at the top
of this document, or to the appropriate forum hosted by Borland.
Please note that according to the newsgroup
guidelines, you should not crosspost or multipost your
message. Please post your message to the single most appropriate
group.
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| About
this FAQ
This document
is compiled and maintained by Jorge
Alvarez from sunny Nuevo Laredo, México. Contributions,
corrections, and comments are welcome and encouraged. |
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