Manuel,
Thanx for the excellent overview of metabase. I will give it a test drive.
A couple further questions, if you have time:
Do you execute meta commands like you do with the other db interface
functions, e.g., odbc_connect(), odbc_select(), etc., or are you able to
encapsulate SQL between tags, e.g.
<tag>
SELECT bar FROM foo WHERE barname = "chocolate";
</tag>
Using a function set can be cumbersome, compared to embedded language
interfaces where you just put SQL between tags, just like PHP is handled
between the <? ?> tags.
Also, can you PREPARE, DECLARE, and OPEN cursors like, say, in Informix, so
you can use variable SELECT parameters? For example, using Informix ESQL/C
you can PREPARE a statement, use it to DECLARE a CURSOR, and the OPEN the
CURSOR USING multiple values, as in:
sprintf( query, "%s %s %s %s %s %s %s %s %s",
"begin work;",
"update account set balance = balance + ?,"
"where acct_number = ?;",
"update teller set balance = balance + ?",
"where teller_number = ?;",
"update brance set balance = balance + ?",
"where branch_number = ?;"
"insert into history values (?, ?);",
"commit work;" );
$prepare qid from $query;
$execute qid using $delta, $acct_number, $delta, $teller_number,
$delta, $branch_number, $timestamp, $values;
I should be able to check metabase out later this evening. If it can handle
the above native database language, I think it will be an asset, especially
for some of our older applications.
Thanx again,
James Potts
"Manuel Lemos" <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> Hello,
>
> James wrote:
> > Regarding a database abstraction package: does Metabase handle all
> > "standard" SQL constructs (as opposed to vendor-specific SQL
extensions)?
> > The GUI applications to be ported were built with JAM, which basically
> > provides an abstraction layer via its JPL language. JPL has not been
> > restrictive in terms of required functionality, nor was there any real
> > performance hits. Can the same be said of Metabase? Also, would
Metabase
> > present a significant learning curve for experienced C and SQL
programmers?
> >
> > I will download PostgreSQL and check it out.
>
> Metabase does much more than you probably may want. Basically you can
> just submit any queries to the database server. Metabase doesn't touch
> them. What it does is when you are composing your queries with constant
> values, it may convert the respective data type values from a database
> independent data type set to the target database data types.
>
> Let's say you have strings or date constant values. Each database may
> have different ways to escape strings or format dates. Metabase provides
> functions to do that translation if you want to use direct queries. I
> you want to use prefered queries, with placeholders ( ? ) in the queries
> that are replace with constant values when the queries are executed, the
> functions to set those values perform the translations for you.
>
> For retrieving result data returned by SELECT queries, Metabase also
> provides functions to translate the data to a database independent
> format, so in your applications you only have to handle one universal
> format that you do not need to adapt if you decide to switch to your
> database backend.
>
> That is not all. Metabase also provides unique features, that are very
> important for Web programming, all in a database independent way. One is
> the ability to create and access to database sequence objects. Sequences
> are objects that can generate sequential integer unique numbers. They
> are often used to generate id values for table primary keys. Sequence
> number generation is guaranteed to be atomic, so it is adequate for
> environments where many users access the database concurrently, like the
> Web. Sequences are implemented with real sequence objects in databases
> that support it like Oracle and Postgres, but others that don't support
> real sequence objects are emulated with tables with a single
> auto-incremented integer field.
>
> Another important feature is the ability for Web programming is the
> ability to limit the range of rows that are returned from a select
> query, like MySQL LIMIT clause, but in a way that is supported by all
> databases supported by Metabase. This is great to let you develop
> applications that display query results split in multiple pages if they
> have too many rows.
>
> Metabase is not also good for develop applications to access databases.
> It is also able to install databases for you creating tables, fields,
> indexes and sequence from a database independent schema description
> defined in a specific XML format. Also, if later you need to change your
> database schema, all you need to do is change the schema description XML
> file. Metabase manager is able to figure the differences between the new
> and the previously installed schema and then it just alters the database
> without affecting the data that was stored after the database was
> installed for the first time or changed for the last time. This saves
> you toons of hours and maintenance headache.
>
> Metabase is easy to learn. In the site there is a tutorial document that
> get you started real quick. If you need further help, you may join to
> the Metabase development mailing list that is listed in the Metabase
> page links sections. Look also in the database section of the PHP
> Classes site for components ready to use with Metabase.
>
> Regards,
> Manuel Lemos
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