view release on metacpan or  search on metacpan

Informix.pm  view on Meta::CPAN

If $dbh->{PrintError} is false, then DBI does not report any errors when
it detects them; the user must note that errors have occurred and decide
whether to report them.

If you connect using the DBI->connect() method, or if you have forgotten
the driver, you can discover it again using:

    $drh = $dbh->{Driver};

This statement allows you to access the driver methods and attributes
described previously.

The name of the current database for a given database handle is tracked
accurately even when the DATABASE, CLOSE DATABASE, CREATE DATABASE,
ROLLFORWARD DATABASE, and START DATABASE statements are used.
Note that you cannot prepare CONNECT statements, so they do not have to
be tracked.
Except when using ESQL/C 5.x, you cannot use the database statements
listed above if you connect directly to a database, so the statements do
not have to be tracked very often - you must have connected to the
server alone.

Note that DBD::Informix allows you to obtain any of the driver
attributes from a database handle too.

=head2 METADATA

You can call two methods using the DBI func() to get
at some basic Informix metadata relatively conveniently.

    @list = $dbh->func('_tables');
    @list = $dbh->func('user', '_tables');
    @list = $dbh->func('base', '_tables');
    @list = $dbh->func('user', 'base', '_tables');
    @list = $dbh->func('system', '_tables');
    @list = $dbh->func('view', '_tables');
    @list = $dbh->func('synonym', '_tables');

The lists of tables are all qualified as "owner".tablename, and you
can use them in SQL statements without fear that the table is not
present in the database (unless someone deletes it behind your back).
The leading arguments qualify the list of names returned.
Private synonyms are reported for just the current user.

    @list = $dbh->func('_columns');
    @list = $dbh->func(@tables, '_columns');

The lists are each references to an array of values corresponding to
the owner name, table name, column number, column name, basic
data type (C<ix_ColType> value--see below), and data length
(C<ix_ColLength> value--see below).
If no tables are listed, all columns in the database are listed.
This can be quite slow because handling synonyms properly requires a
UNION operation.
Further, although the '_tables' method reports the names of remote
synonyms, the '_columns' method does not expand them (mainly because
it is very hard to do properly).
See the examples in t/t55mdata.t for how to use these methods.
Exercise for the reader: Extend '_columns' to get reports on the
columns in remote synonyms, including relocated remote synonyms where
the original referenced site now forwards the name to a third site!

See also C<DBD::Informix::Metadata(3)>.

=head2 DISCONNECTING FROM A DATABASE

You can also disconnect from the database:

    $dbh->disconnect;

The previous example will roll back any uncommitted work.
Note that this example does not destroy the database handle.
You need to do an explicit 'undef $dbh' to destroy the handle.
Any statements you prepare with this handle are finished (see below)
and cannot be used again.
All space associated with the statements is released.

If you are using an Informix driver for which $drh->{ProductVersion}
>= 600, you can have multiple concurrent connections (subject to the
normal Informix constraint that a single process can have at most one
shared memory connection open at any time).
This means that multiple calls to $drh->connect will give you
independent connections to one or more databases.

If you are using an Informix driver for which $drh->{ProductVersion} <
600, you cannot have multiple concurrent connections.
If you make multiple calls to $drh->connect, you will achieve the same
effect as if you execute several database statements in a row.
Multiple calls to $drh->connect will generally switch databases
successfully but will invalidate any statements you previously
prepared.
Multiple calls to $drh->connect might fail in instances when the
current database is not local or when there is an active transaction.

=head2 SIMPLE STATEMENTS

Given a database connection, you can execute a variety of simple
statements with a variety of different calls:

    $dbh->commit;
    $dbh->rollback;

These two operations commit or roll back the current transaction.
If the database is unlogged, the two operations do nothing.
If AutoCommit is set to 1, the two operations do nothing useful.
If AutoCommit is set to 0, a new transaction is started
(implicitly for a database that is MODE ANSI, explicitly for a
database that is not MODE ANSI).

To execute most preparable parameterless statements you can use:

    $dbh->do($stmt);

The statement must be neither a SELECT statement other than
SELECT...INTO TEMP nor an EXECUTE PROCEDURE statement where the
procedure returns data.

You can execute an arbitrary statement with parameters using:

    $dbh->do($stmt, undef, @parameters);