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Alzabo::SQLMaker - Alzabo base class for RDBMS drivers |
Alzabo::Table and/or Alzabo::Column objects)Alzabo::Table)Alzabo::Table object, ...)Alzabo::Table object(s) and/or $string(s))Alzabo::Column object or SQL function), $comparison, (Alzabo::Column object, $value, or Alzabo::SQLMaker object), [ see below ] )where)where)Alzabo::Column objects)Alzabo::Table object, optional Alzabo::Column objects)Alzabo::Column object => $value, ...)Alzabo::Column object => $value, ...)
Alzabo::SQLMaker - Alzabo base class for RDBMS drivers
use Alzabo::SQLMaker;
my $sql = Alzabo::SQLMaker->new( sql => 'MySQL' );
This is the base class for all Alzabo::SQLMaker modules. To
instantiate a driver call this class's new method. See
SUBCLASSING Alzabo::SQLMaker for information on how to make a
driver for the RDBMS of your choice.
A list of names representing the available Alzabo::SQLMaker
subclasses. Any one of these names would be appropriate as a
parameter for the Alzabo::SQLMaker->new
method.
Load the specified subclass.
The name of the Alzabo::SQLMaker subclass that was loaded.
This class can be used to generate SQL by calling methods that are the
same as those used in SQL (select, update, etc.) in sequence,
with the appropriate parameters.
There are four entry point methods, select, insert,
update, and delete.
Attempting call any other method without first calling one of these is
an error.
These methods are called as class methods and return a new object.
Alzabo::Table and/or Alzabo::Column objects)This begins a select. The columns to be selected are the column(s)
passed in, and/or the columns of the table(s) passed in as arguments.
Alzabo::Table)
All of these methods return the object itself, making it possible to chain together method calls such as:
Alzabo::SQLMaker->select($column)->from($table)->where($other_column, '>', 2);
Alzabo::Table object, ...)The table(s) from which we are selecting data.
Alzabo::Table object(s) and/or $string(s))There is no publically available method in this class called
** function. This method represents all available SQL functions, such
as COUNT or AVG. The name of the method is the name of the
function to be called. Each subclass knows which functions are legal
for the RDBMS they represent. All the arguments are joined together
by commas (,) internally. Here is a simple example:
Alzabo::SQLMaker->select->count($column)->from($table)->where($other_column, '>', 2);
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 an 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 operator allows any number of additional parameters, which
may be Alzabo::Column objects, values, or Alzabo::SQLMaker
objects.
where)
where)These methods take the same parameters as the
where method. There is currently no way
to group together comparison operators.
Alzabo::Column objects)Adds an ORDER BY clause to your SQL.
Modifies the sorting of an ORDER BY clause.
Specifies a limit on the number of rows to be returned. The offset parameter is optional.
Nothing.
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.
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.
Nothing.
Alzabo::Column object => $value, ...)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 the Alzabo::Driver manpage module takes a limit parameter.
The return value of this method can be passed in as that parameter in
all cases.
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.
To create a subclass of Alzabo::SQLMaker for your particular RDBMS
requires only that the Alzabo::SQLMaker/Virtual Methods in the virtual methods manpage 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.
Dave Rolsky, <dave@urth.org>
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Alzabo::SQLMaker - Alzabo base class for RDBMS drivers |