DBI Interface Specification Version 0.2.1 (Draft)

by Michael Neumann (neumann@s-direknet.de)

$Id: DBI_SPEC.html,v 1.20 2002/04/16 20:39:09 mneumann Exp $

Module DBD

Constants

API_VERSION: Use this in your DBD driver to ensure it is used with the correct DBD API-Version

Module DBI

Constants

VERSION: Version of the DBI Interface
SQL_FETCH_NEXT
SQL_FETCH_PRIOR
SQL_FETCH_FIRST
SQL_FETCH_LAST
SQL_FETCH_ABSOLUTE: Constants for StatementHandle#fetch_scroll.
SQL_BIT
SQL_TINYINT
SQL_SMALLINT
SQL_INTEGER
SQL_BIGINT
SQL_FLOAT
SQL_REAL
SQL_DOUBLE
SQL_NUMERIC
SQL_DECIMAL
SQL_CHAR
SQL_VARCHAR
SQL_LONGVARCHAR
SQL_DATE
SQL_TIME
SQL_TIMESTAMP
SQL_BINARY
SQL_VARBINARY
SQL_LONGVARBINARY
SQL_OTHER: Constant representing SQL types.

Exceptions

Exception classes were "borrowed" from Python API 2.0.

Warning < RuntimeError

For important warnings like data truncation etc.

Error < RuntimeError

Base class of all other error exceptions. Use this to catch all errors.

InterfaceError < Error

Exception for errors related to the DBI interface rather than the database itself.

NotImplementedError < InterfaceError

Exception raised if the DBD driver has not specified a mandantory method (not in Python API 2.0).

DatabaseError < Error

Exception for errors related to the database.

Has three attributes err, errstr and state.

DataError < DatabaseError

Exception for errors due to problems with the processed data like division by zero, numeric value out of range etc.

OperationalError < DatabaseError

Exception for errors related to the database's operation which are not necessarily under the control of the programmer like unexpected disconnect, datasource name not found, transaction could not be processed, a memory allocation error occured during processing etc.

IntegrityError < DatabaseError

Exception raised when the relational integrity of the database is affected, e.g. a foreign key check fails

InternalError < DatabaseError

Exception raised when the database encounters an internal error, e.g. the cursor is not valid anymore, the transaction is out of sync.

ProgrammingError < DatabaseError

Exception raised for programming errors, e.g. table not found or already exists, syntax error in SQL statement, wrong number of parameters specified, etc.

NotSupportedError < DatabaseError

Raised if e.g. commit() is called for a database which do not support transactions.

Module functions

DBI.connect( driver_url, user=nil, auth=nil, params=nil )

Connect to the database specified by driver_url, which may look like "dbi:Oracle:oracle.neumann".

Returns an DBI::DatabaseHandle object, or if called with code-block, calls this block with the new DBI::DatabaseHandle as parameter and calls disconnect after calling the block if it was not yet disconnected by the user.

DBI.available_drivers

Returns an Array of all available DBD driver. The strings which represent a DBD driver are partial DSN's (e.g. "dbi:Oracle:").

DBI.data_sources( driver )

Returns all available DSN's for the driver, which is a partial DSN (e.g. "dbi:Oracle:").

DBI.disconnect_all( driver=nil )

Disconnects all active connections of driver or all drivers if driver is nil.

DBI.trace(mode=nil, output=nil)

Set the trace mode for all following created Handles to these values.

If a parameter is nil the value is not changed. mode defaults to 2 if it is nil, and output to STDERR if a value was not set before. For mode the values 0, 1, 2 or 3 are allowed.

Note: Tracing is only activated, if you load the module "dbi/trace", because tracing currently depends on AspectR > 0.3.3.

Class DBI::Handle

Abstract base class for all "Handles" (DriverHandle, DatabaseHandle, StatementHandle).

Instance Methods

func( function, *values )

Calls the driver specific extension function named by function with values as parameters.

trace(mode=nil, output=nil)

Set the trace mode for this handle as well as for all sub-handles (in the case of DriverHandle and DatabaseHandle).

If a parameter is nil the value is not changed. mode defaults to 2 if it is nil, and output to STDERR if a value was not set before. For mode the values 0, 1, 2 or 3 are allowed.

Note: Tracing is only activated, if you load the module "dbi/trace", because tracing currently depends on AspectR > 0.3.3.

Class DBI::DatabaseHandle

Superclass

DBI::Handle

Instance Methods

connected?

Returns true if the connection was not yet disconnected by calling disconnect, otherwise false.

disconnect

Disconnects the connection.

prepare( stmt )

prepare( stmt ) {|statement_handle| aBlock}

Prepare the SQL statement stmt and return a DBI::StatementHandle or if called with a code-block calls the block with the handle as parameter and after that calls #finish onto the handle to free all resources

execute( stmt, *bindvars )

execute( stmt, *bindvars ) {|statement_handle| aBlock}

Executes immediately the SQL statement stmt with binding the placeholders with values given in bindvars before.

Returns a DBI::StatementHandle or if called with code-block calls the block with the handle as parameter and after that calls #finish onto the handle to free all resources.

do( stmt, *bindvars )

Same as execute only that no DBI::StatementHandle is returned but the RPC (Row Processed Count).

select_one( stmt, *bindvars)

Executes the statement with binding the values to the parameters and returns the first row as a reference to a Row object.

select_all( stmt, *bindvars)

Executes the statement with binding the values to the parameters and returns all resulting rows.

If called as iterator the passed DBI::Row objects are only references.

tables

Returns a list of all tables and views.

columns( table )

Get more information about the columns of table table. Returns an array containing for each column one DBI::ColumnInfo object.

ping

Returns true if the connection is active, otherwise false.

In contranst to connected?, ping tests if the connection is still active by executing some SQL or doing something else.

quote( value )

Quotes the given value value database specific and returns the result.

commit

Commits current transaction.

rollback

Rolls the current transaction back.

transaction {|database_handle| aBlock}

First commits the current transaction, then executes the given block where the parameter is the object itself (the database handle). If the block raises an exception, then it rolls the transaction back otherwise commits it.

[attr]

[attr] = val

Sets or gets the attribute attr. An attribute can for example be "AutoCommit", which can be set to true or false. Attributes are database dependant.

Class DBI::StatementHandle

Bind param which is either a String which is then the name of the placeholder used in the SQL statement (e.g. Oracle: "SELECT * FROM EMP WHERE ENAME = :ename") or it is an integer which is then the number of the placeholder where counting starts at 1.

value is the value which is bound to the placeholder.

attribs is not yet used in this version, but could later be a hash containing more information like parameter type etc..

execute( *bindvars )

Execute the statement but before binds the placeholders with bindvars.

finish

Frees the resources for the statement. After calling finish no other operation on this statement is valid.

cancel

Frees any result set resources which were made after a call to execute. After calling this method, a call to one of the fetch methods is no more valid.

column_names

Returns an Array of all column names.

column_info

Returns an Array containing fore each column one DBI::ColumnInfo object.

rows

Returns the RPC (Row Processed Count) of the last executed statement, or nil if no such exist.

fetchable?

Returns true if you can fetch rows using fetch etc..

fetch

Returns a DBI::Row object, or nil if there are no more rows to fetch.

When called as iterator, the block is called for each row until no more row is available. Each row is passed to the block as DBI::Row object.

Note that the returned or passed DBI::Row object is only a reference and should be copied (dup) if it is store elsewhere.

each {|row| aBlock }

Same as fetch called as iterator.

fetch_array

Returns the current row as Array or nil if no more row is available.

Can be also called as iterator.

fetch_hash

Returns the current row as Hash or nil if no more row is available.

Can be also called as iterator.

fetch_many( cnt )

Returns an Array of the next cnt rows, which are stored as DBI::Row objects.

Returns the empty array [] if there are no more rows.

fetch_all

Same as fetch_many only that all rows are returned.

fetch_scroll( direction, offset=1 )

direction is one of the following constants:

SQL_FETCH_NEXT
SQL_FETCH_PRIOR
SQL_FETCH_FIRST
SQL_FETCH_LAST
SQL_FETCH_ABSOLUTE
SQL_FETCH_RELATIVE

offset is a positive or negativ number (only when SQL_FETCH_RELATIVE is used).

fetch_scroll do not automatically free the result set if no more rows are available if e.g. you get the last row.

Returns a DBI::Row object, if not possible, returns nil.

Note that the returned DBI::Row object is only a reference and should be copied (dup) if it is stored elsewhere.