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DBIx-DBStag-0.02
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/ DBIx::DBStag::SQLTemplate

NAME

DBIx::DBStag::SQLTemplate - A Template for an SQL query

SYNOPSIS

# find template by name
$template = $dbh->find_template("mydb-personq");

# execute this template, filling in the 'name' attribute
$xml = $dbh->selectall_xml(-template=>$template, 
                           -bind=>{name => "fred"});

DESCRIPTION

A template represents a canned query that can be parameterized.

Templates are collected in directories (in future it will be possible to store them in files or in the db itself).

To tell DBStag where your templates are, you should set:

setenv DBSTAG_TEMPLATE_DIRS "$HOME/mytemplates:/data/bioconf/templates"

Your templates should end with the suffix .stg, otherwise they will not be picked up

You can name templates any way you like, but the standard way is to use 2 or 3 fields

SCHEMA-OBJECT

or

SCHEMA-OBJECT-QUALIFIERS

(with underscores used within fields)

A template file should contain at minimum some SQL; for example:

Example template 1
SELECT 
             studio.*,
             movie.*,
             star.*
FROM
             studio NATURAL JOIN 
             movie NATURAL JOIN
             movie_to_star NATURAL JOIN
             star
WHERE
             [movie.genre = &genre&] [star.lastname = &lastname&]
USE NESTING (set(studio(movie(star))))

Thats all! However, there are ways to make your template more useful

Example template 2
:SELECT 
             studio.*,
             movie.*,
             star.*
:FROM
             studio NATURAL JOIN 
             movie NATURAL JOIN
             movie_to_star NATURAL JOIN
             star
:WHERE
             [movie.genre = &genre&] [star.lastname = &lastname&]
:USE NESTING (set(studio(movie(star))))

//
schema: movie
desc: query for fetching movies

By including : at the beginning it makes it easier for parsers to assemble SQL (this is not necessary for DBStag however)

After the // you can add tag: value data.

You should set schema: if you want the template to be available to users of a db that conforms to that schema

GETTING A TEMPLATE

The DBIx::DBStag object gives various methods for fetching templates by name, by database or by schema

VARIABLES

WHERE clause variables in the template look like this

&foo&

variables are bound at query time

my $set = $dbh->selectall_stag(-template=>$t,
                               -bind=>["bar"]);

or

my $set = $dbh->selectall_stag(-template=>$t,
                               -bind=>{foo=>"bar"});

If the former is chosen, variables are bound from the bind list as they are found

OPTIONAL BLOCKS

WHERE [ foo = &foo& ]

If foo is not bound then the part between the square brackets is left out

Multiple option blocks are ANDed together

An option block need not contain a variable - if it contains no &variable& name it is automatically ANDed

BINDING OPERATORS

The operator can be bound at query time too

WHERE [ foo => &foo& ]

Will become either

WHERE foo = ?

or

WHERE foo LIKE ?

or

WHERE foo IN (f0, f1, ..., fn)

Depending on whether foo contains the % character, or if foo is bound to an ARRAY

METHODS

name

Usage   - $name = $template->name
Returns - str
Args    -

every template has a name that (should) uniquely identify it

desc

Usage   - $desc = $template->desc
Returns - str
Args    -

templates have optional descriptions

get_varnames

Usage   - $varnames = $template->get_varnames
Returns - listref of strs
Args    -

Returns the names of all variable used in this template

WEBSITE

http://stag.sourceforge.net

AUTHOR

Chris Mungall <cjm@fruitfly.org>

COPYRIGHT

Copyright (c) 2003 Chris Mungall

This module is free software. You may distribute this module under the same terms as perl itself