Alzabo::Exceptions(3pm) User Contributed Perl Documentation Alzabo::Exceptions(3pm)NAME
Alzabo::Exceptions - Creates all exception subclasses used in Alzabo.
SYNOPSIS
use Alzabo::Exceptions;
DESCRIPTION
Using this class creates all the exceptions classes used by Alzabo (via the "Exception::Class" class).
See "Exception::Class" for more information on how this is done.
EXCEPTION CLASSES
* Alzabo::Exception
This is the base class for all exceptions generated within Alzabo (all exceptions should return true for "$@->isa('Alzabo::Exception')"
except those that are generated via internal Perl errors).
* Alzabo::Exception::Driver
An error occured while accessing a database. See "Alzabo::Driver" for more details.
* Alzabo::Exception::Eval
An attempt to eval something returned an error.
* Alzabo::Exception::Logic
Alzabo was asked to do something logically impossible, like retrieve rows for a table without a primary key.
* Alzabo::Exception::NoSuchRow
An attempt was made to fetch data from the database with a primary key that does not actually exist in the specified table.
* Alzabo::Exception::NotNullable
An attempt was made to set a non-nullable column to "NULL". The "column_name", "table_name", and "schema_name" fields can be used to
identify the exact column.
* Alzabo::Exception::Panic
This exception is thrown when something completely unexpected happens (think Monty Python).
* Alzabo::Exception::Params
This exception is thrown when there is a problem with the parameters passed to a method or function. These problems can include miss-
ing parameters, invalid values, etc.
* Alzabo::Exception::RDBMSRules
A rule for the relevant RDBMS was violated (bad schema name, table name, column attribute, etc.)
* Alzabo::Exception::ReferentialIntegrity
An insert/update/delete was attempted that would violate referential integrity constraints.
* Alzabo::Exception::SQL
An error thrown when there is an attempt to generate invalid SQL via the Alzabo::SQLMaker module.
* Alzabo::Exception::Storable
A error when trying to freeze, thaw, or clone an object using Storable.
* Alzabo::Exception::System
Some sort of system call (file read/write, stat, etc.) failed.
* Alzabo::Exception::VirtualMethod
A virtual method was called. This indicates that this method should be subclassed.
AUTHOR
Dave Rolsky, <autarch@urth.org>
perl v5.8.8 2007-12-23 Alzabo::Exceptions(3pm)
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Alzabo::SQLMaker(3pm) User Contributed Perl Documentation Alzabo::SQLMaker(3pm)NAME
Alzabo::SQLMaker - Alzabo base class for RDBMS drivers
SYNOPSIS
use Alzabo::SQLMaker::MySQL;
my $sql = Alzabo::SQLMaker::MySQL->new( driver => $driver_object );
# or better yet
my $sql = $runtime_schema->sqlmaker;
DESCRIPTION
This is the base class for all Alzabo::SQLMaker modules. To instantiate a driver call this class's "new" method. See "SUBCLASSING Alz-
abo::SQLMaker" for information on how to make a driver for the RDBMS of your choice.
METHODS
available
Returns A list of names representing the available "Alzabo::SQLMaker" subclasses. Any one of these names would be appropriate as a parame-
ter for the "Alzabo::SQLMaker->load()" method.
load
Load the specified subclass.
This takes one parameter, the name of the RDBMS being used.
Throws: "Alzabo::Exception::Eval"
new
This takes two parameters:
* driver
The driver object being used by the schema.
* quote_identifiers
A boolean value indicating whether or not identifiers should be quoted. This defaults to false.
GENERATING SQL
This class can be used to generate SQL by calling methods that are the same as those used in SQL ("select()", "update()", etc.) in
sequence, with the appropriate parameters.
There are four entry point methods, "select()", "insert()", "update()", and "delete()". Attempting to call any other method without first
calling one of these is an error.
Entry Points
These methods are called as class methods and return a new object.
select ("Alzabo::Table" and/or "Alzabo::Column" objects)
This begins a select. The columns to be selected are the column(s) passed in, and/or the columns of the table(s) passed in as arguments.
Followed by:
"from()"
"** function"
insert
Followed by:
"into()"
update ("Alzabo::Table")
Followed by:
"set()"
delete
Followed by:
"from()"
Other Methods
All of these methods return the object itself, making it possible to chain together method calls such as:
Alzabo::SQLMaker->select($column)->from($table)->where($other_column, '>', 2);
from ("Alzabo::Table" object, ...)
The table(s) from which we are selecting data.
Follows:
"select()"
"** function"
"delete()"
Followed by:
"where()"">
"order_by()"
Throws: "Alzabo::Exception::SQL"
where <see below>
The first parameter to where must be an "Alzabo::Column" object or SQL function. The second is a comparison operator of some sort, given
as a string. The third argument can be an "Alzabo::Column" object, a value (a number or string), or an "Alzabo::SQLMaker" object. The
latter is treated as a subselect.
Values given as parameters will be properly quoted and escaped.
Some comparison operators allow additional parameters.
The "BETWEEN" comparison operator requires a fourth argument. This must be either an "Alzabo::Column" object or a value.
The "IN" and <NOT IN> operators allow any number of additional parameters, which may be "Alzabo::Column" objects, values, or "Alzabo::SQL-
Maker" objects.
Follows:
"from()"
Followed by:
"and()"
"or()"
"order_by()"
Throws: "Alzabo::Exception::SQL"
and (same as "where")
or (same as "where")
These methods take the same parameters as the "where()""> method.
Follows:
"where()"">
"and()"
"or()"
Followed by:
"and()"
"or()"
"order_by()"
Throws: "Alzabo::Exception::SQL"
order_by ("Alzabo::Column" objects)
Adds an "ORDER BY" clause to your SQL.
Follows:
"from()"
"where()"">
"and()"
"or()"
Followed by:
"limit()"
Throws: "Alzabo::Exception::SQL"
limit ($max, optional $offset)
Specifies a limit on the number of rows to be returned. The offset parameter is optional.
Follows:
"from()"
"where()"">
"and()"
"or()"
"order_by()"
"Alzabo::Exception::SQL"
into ("Alzabo::Table" object, optional "Alzabo::Column" objects)
Used to specify what table an insert is into. If column objects are given then it is expected that values will only be given for that
object. Otherwise, it assumed that all columns will be specified in the "values()" method.
Follows:
"insert()"
Followed by:
"values()"
Throws: "Alzabo::Exception::SQL"
values ("Alzabo::Column" object => $value, ...)
This method expects to recive an structured like a hash where the keys are "Alzabo::Column" objects and the values are the value to be
inserted into that column.
Follows:
"into()"
Throws: "Alzabo::Exception::SQL"
set ("Alzabo::Column" object => $value, ...)
This method'a parameter are exactly like those given to the "values" method.
Follows:
"update()"
Followed by:
"where()"">
Throws: "Alzabo::Exception::SQL"
RETRIEVING SQL FROM THE OBJECT
sql
This method can be called at any time, though obviously it will not return valid SQL unless called at a natural end point. In the future,
an exception may be thrown if called when the SQL is not in a valid state.
Returns the SQL generated so far as a string.
bind
Returns an array reference containing the parameters to be bound to the SQL statement.
SUBCLASSING Alzabo::SQLMaker
To create a subclass of "Alzabo::SQLMaker" for your particular RDBMS requires only that the virtual methods listed below be implemented.
In addition, you may choose to override any of the other methods described in this documentation. For example, the MySQL subclass override
the "_subselect()" method because MySQL cannot support sub-selects.
Subclasses are also expected to offer for export various sets of functions matching SQL functions. See the "Alzabo::SQLMaker::MySQL" sub-
class implementation for details.
VIRTUAL METHODS
The following methods must be implemented by the subclass:
limit
See above for the definition of this method.
get_limit
This method may return "undef" even if the "limit()" method was called. Some RDBMS's have special SQL syntax for "LIMIT" clauses. For
those that don't support this, the "Alzabo::Driver" module takes a "limit" parameter.
The return value of this method can be passed in as that parameter.
If the RDBMS does not support "LIMIT" clauses, the return value is an array reference containing two values, the maximum number of rows
allowed and the row offset (the first row that should be used).
If the RDBMS does support "LIMIT" clauses, then the return value is "undef".
sqlmaker_id
Returns the subclass's name. This should be something that can be passed to "Alzabo::SQLMaker->load()" as a parameter.
AUTHOR
Dave Rolsky, <dave@urth.org>
perl v5.8.8 2007-12-23 Alzabo::SQLMaker(3pm)