Alzabo::SQLMaker - Alzabo base class for RDBMS drivers
use Alzabo::SQLMaker; my $sql = Alzabo::SQLMaker->new( sql => 'MySQL' );
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.
new
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.
Alzabo::SQLMaker
Alzabo::SQLMaker->new
Load the specified subclass.
rdbms => $rdbms
The name of the RDBMS being used.
The name of the Alzabo::SQLMaker subclass that was loaded.
Alzabo::Exception::Eval
This class can be used to generate SQL by calling methods that are the same as those used in SQL (select, update, etc.) in sequence, with the appropriate parameters.
select
update
There are four entry point methods, select, insert, update, and delete. Attempting call any other method without first calling one of these is an error.
insert
delete
These methods are called as class methods and return a new object.
Alzabo::Table
Alzabo::Column
This begins a select. The columns to be selected are the column(s) passed in, and/or the columns of the table(s) passed in as arguments.
from
** function
into
set
All of these methods return the object itself, making it possible to chain together method calls such as:
Alzabo::SQLMaker->select($column)->from($table)->where($other_column, '>', 2);
The table(s) from which we are selecting data.
where
order_by
Alzabo::Exception::SQL
There is no publically available method in this class called ** function. This method represents all available SQL functions, such as COUNT or AVG. The name of the method is the name of the function to be called. Each subclass knows which functions are legal for the RDBMS they represent. All the arguments are joined together by commas (,) internally. Here is a simple example:
COUNT
AVG
Alzabo::SQLMaker->select->count($column)->from($table)->where($other_column, '>', 2);
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.
BETWEEN
The IN operator allows any number of additional parameters, which may be Alzabo::Column objects, values, or Alzabo::SQLMaker objects.
IN
and
or
These methods take the same parameters as the where method. There is currently no way to group together comparison operators.
Adds an ORDER BY clause to your SQL.
ORDER BY
asc
desc
Modifies the sorting of an ORDER BY clause.
limit
Specifies a limit on the number of rows to be returned. The offset parameter is optional.
Nothing.
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.
values
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.
This method'a parameter are exactly like those given to the values method.
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.
The SQL generated so far.
An array reference containing the parameters to be bound to the SQL statement.
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" in Alzabo::Driver module takes a limit parameter. The return value of this method can be passed in as that parameter in all cases.
LIMIT
Alzabo::Driver
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.
undef
To create a subclass of Alzabo::SQLMaker for your particular RDBMS requires only that the "Alzabo::SQLMaker/Virtual Methods" in 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.
_subselect
Dave Rolsky, <dave@urth.org>
To install Alzabo, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Alzabo
CPAN shell
perl -MCPAN -e shell install Alzabo
For more information on module installation, please visit the detailed CPAN module installation guide.