Take me over?
NAME
Alzabo::SQLMaker - Alzabo base class for RDBMS drivers
SYNOPSIS
use Alzabo::SQLMaker;
my $sql = Alzabo::SQLMaker->new( sql => 'MySQL' );DESCRIPTION
This is the base class for all Alzabo::SQLMaker modules. To instantiate a driver call this class's new method. See "SUBCLASSING Alzabo::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 parameter for the Alzabo::SQLMaker->new method.
load
Load the specified subclass.
Parameters
rdbms => $rdbms
The name of the RDBMS being used.
Returns
The name of the Alzabo::SQLMaker subclass that was loaded.
Throws
GENERATING SQL
This class can be used to generate SQL by calling methods that are the same as those used in SQL (select, update, etc.) in sequence, with the appropriate parameters.
There are four entry point methods, select, insert, update, and delete. Attempting call any other method without first calling one of these is an error.
Entry Points
These methods are called as class methods and return a new object.
select (Alzabo::Table and/or Alzabo::Column objects)
This begins a select. The columns to be selected are the column(s) passed in, and/or the columns of the table(s) passed in as arguments.
Followed by
insert
Followed by
update (Alzabo::Table)
Followed by
delete
Followed by
Other Methods
All of these methods return the object itself, making it possible to chain together method calls such as:
Alzabo::SQLMaker->select($column)->from($table)->where($other_column, '>', 2);from (Alzabo::Table object, ...)
The table(s) from which we are selecting data.
Follows
Followed by
Throws
where ( (Alzabo::Column object or SQL function), $comparison, (Alzabo::Column object, $value, or Alzabo::SQLMaker object), [ see below ] )
The first parameter must be an Alzabo::Column object or SQL function. The second is a comparison operator of some sort, given as a string. The third argument can be one of three things. It can be an Alzabo::Column object, a value (a number or string), or an Alzabo::SQLMaker object. The latter is treated as a subselect.
Values given as parameters will be properly quoted and escaped.
Some comparison operators allow additional parameters.
The BETWEEN comparison operator requires a fourth argument. This must be either an Alzabo::Column object or a value.
The IN and <NOT IN> operators allow any number of additional parameters, which may be Alzabo::Column objects, values, or Alzabo::SQLMaker objects.
Follows
Followed by
Throws
and (same as where)
or (same as where)
These methods take the same parameters as the where method. There is currently no way to group together comparison operators.
Follows
Followed by
Throws
order_by (Alzabo::Column objects)
Adds an ORDER BY clause to your SQL.
Follows
Followed by
Throws
limit ($max, optional $offset)
Specifies a limit on the number of rows to be returned. The offset parameter is optional.
Follows
Followed by
Nothing.
Throws
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
Followed by
Throws
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
Followed by
Nothing.
Throws
set (Alzabo::Column object => $value, ...)
This method'a parameter are exactly like those given to the values method.
Follows
Followed by
Throws
Retrieving SQL
sql
This 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.
bind
Returns
An array reference containing the parameters to be bound to the SQL statement.
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 in all cases.
Returns
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.
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 listed in over-rideable methods. For example, the MySQL subclass override the _subselect method because MySQL cannot support sub-selects.
Virtual Methods
AUTHOR
Dave Rolsky, <dave@urth.org>