Drupal - dbtng 25th Anniversary Edition

Drupal DataBase
The next Generation

Drupal for the Enterprise.
Austin Drupal User’s Group

David Diers, Developer
Four Kitchens
Austin, TX

D.O - thebruce
@beautyhammer

What we’ll cover
!   Basics of the Drupal DB API
!   Using db_query
!   Using and building dynamic queries including
!  Criteria clauses, joins, sorting, sub-selects,
extenders, and tagging
!   How to work with result sets

Drupal and the DB
!   Drupal uses the DB to:
!  Store content - where
"content" is thought of very
broadly.
!  Store user or module
configurations
!  Store system values
!   Drupal retrieves these values
all of the time.

Drupal and DB Abstraction
!   What is DB Abstraction?
!  Uniformity
!  Structure
!   DB Abstraction is nothing new for Drupal

Drupal 7 DB API uses PDO
!   D7 had a facelift for DB Layer
!   Built on PDO
!  PDO is PHPOOP
!  Drupal extends PDO classes
!  PDO used in many projects

It takes some learning. So
why learn the DB API?
!   You may say, with all due
respect:
!  Isn’t most of this stuff in
functions already?
!  Doesn’t views do this for
me?
!  Can’t I just use raw SQL
like they did in ye olde
days™?

A few reasons:
!   Need a result set that you can’t get or requires custom
views development?
!   Writing or supporting custom modules with their own
schema?
!   Need results from the contrib module’s schema but there
isn’t a function to do so?
!   Patching an existing modules’ database functionality?
!   Need additional ways besides exportables (features, views,
panels) to migrate configuration via update hooks?
!   Need to implement custom sql statements to improve the
performance of your site?

Using the DB API
!   2 Primary ways to interact
with data in D7
! Dbquery
!  Dynamic queries

db_query – the basics
!   IN SQL: !   IN db_query:
<?php
$type = ‘article’;
SELECT nid, title $result = db_query("SELECT nid, title
FROM node FROM {node}
WHERE type = ‘article’; WHERE type = :type", array(':type' =>
$type,));

db_query – the breakdown
$result = db_query("SELECT nid, title FROM {node} WHERE type = :type",
array(':type' => $type,));

! db_query($query, $placeholders, $options)
!   enclose tables in { }
!   Placeholders start with ":"
!  EX: WHERE type = :type", array(':type' => 'page',))
!   Options array - 2 common ones are:
!  Target (default or slave)
!  Fetch (pdo fetch type)

http://druptest7.dev:8888/example_dbq

db_query d6 => d7
transitions
!   In transitioning D6 db_query to D7 be aware:
!  The syntax signature has changed –
•  D6 parameters were less orderly
•  % syntax for placeholders
•  Lawless, unregulated SQL could be executed like a
dishonorable Klingon

Dynamic sql – the basics
!   Dynamic Queries
!  Much more transportable, powerful, but complex
!  You MUST use for ( INSERT, UPDATE,
DELETE)
!  You may use for (SELECT)
•  http://www.lullabot.com/articles/simplify-your-code-
with-drupal-7s-database-api ).

db_select – the basics
!   IN SQL: !   IN db_select:
<?php
SELECT nid, title $query = db_select(‘node’, ’n’);
FROM node $result = $query->fields(‘n’,
WHERE type = ‘article’; array(‘nid’,’title’)
->condition(‘n.type’,$type)
->execute();

Note: This is an example for comparison, selects are better served by dbquery.

db_select – the basics
!   IN db_select:
<?php
(‘node’, ‘n’)
$query = db_select(‘node’, ’n’);
Name of Table / Alias

(fields(‘n’, array(‘nid’,
$result = $query->fields(‘n’,
‘title’))
array(‘nid’,’title’)
Alias, array of fields
->execute();

Single quotes are
important for
transferability.

DQ– of special note
$query = db_select(‘node’, ’n’);
$result = $query->fields(‘n’, array(‘nid’,’title’)
->execute();

!   Fluid Interface
!   ->execute();
!   Returns a result set / statement object

Working with Result Sets
!   Use - foreach loop or
!   or - Specificaly get the next record
!  $record = $result->fetch(); // Use the default fetch
mode.
!   $record = $result->fetchObject(); // Fetch as a
stdClass object.
!   $record = $result->fetchAssoc(); // Fetch as an
associative array.
!   or - to get a single field
!  $record = $result->fetchField($column_index);

But which should I use?

dbquery or dynamic query

Questions to help decide
!   Is your query static? Use db_query it is faster.
!   Does your query need to be constructed at run
time? Use dynamic queries
!   Do you need to INSERT, UPDATE, or DELETE?
Use Dynamic queries.

More with Dynamic Queries
!   How to add fields or select *
!   Conditional Statements
!   AND / OR
!   Sub-selects
!   JOINS
!   SORT

Working with Fields
!   Adding fields to a query:
$query->fields('n', array('nid',
'title', 'created', 'uid'));

"select *" is fields with no
field array indicated:
$query->fields('n');

http://druptest7.dev:8888/example_dyn

Conditional Statements
!   Signature: $query->condition($field, $value = NULL,
$operator = '=')
Default operator is SQL =
!   can take ANSI sql comparators <, >, LIKE, = >=
!  EX: $query->condition('nid',1)
!  EX: $query->condition('nid',1, '<>')
!   In or between:
!  EX: $query->condition('myfield', array(1, 2, 3), 'IN');

Conditional Statements
(more)
!   Nested Conditionals:
db_and() / db_or() / db_xor() are used to handle
nested conditionals such as:
->condition(db_or()
->condition('field2', 5)
->condition('field3', 6))

Testing for NULL:
$query->isNull('myfield');
$query->isNotNull('myfield');

An example from contrib…
!   Original d6 query:
$result = db_query('SELECT * FROM {users}
WHERE ((access <> 0 AND login <> 0 AND access
< (%d - %d)) OR (login = 0 AND created < (%d -
%d))) AND uid <> 1', REQUEST_TIME, $warn_time,
REQUEST_TIME, $warn_time);

…ah, contrib.

Now In dynamic query format
!   $query = db_select('users', 'u');
!   $query->fields('u', array('uid', 'name', 'mail', 'created', 'access'))
!   ->condition(db_or()
!   ->condition(db_and()
!   ->condition('u.access', 0, '<>')
!   ->condition('u.login', 0, '<>')
!   ->condition('u.access', REQUEST_TIME - $warn_time, '<'))
!   ->condition(db_and()
!   ->condition('u.login', 0)
!   ->condition('u.created', REQUEST_TIME - $warn_time, '<'))
!   )
!   ->condition('u.uid', 1, '<>');

!  $results = $query->execute();

Subselects
! Subselects - form a query using dbtng then instead
of executing it -
!   use that query variable in a condition.
!  Best when:
•  one value is returned,
•  A column return value is used with an IN clause.
!   $query->condition('myfield', $querysubselect, 'IN');

JOINS & db_select
<?php
$query = db_select('node', 'n');
$query->join('field_data_body', 'b', 'n.nid = b.entity_id');
$query
->fields('n', array('nid', 'title'))
->condition('n.type', 'page')
->condition('n.status', '1')
->orderBy('n.created', 'DESC')
->addTag('node_access');
?>

dynamic queries: sorting
! orderBy(‘field’, ‘ASC’/’DESC’)

$result = db_select(‘node’, ‘n’)
->fields(‘n’, array(‘title’))
->orderBy(‘n.created’, ‘DESC’)
->execute();

db_select Tagging
Tagging – lets alter hooks take action

ex: $query->addTag('node_access'); - this should be
implemented on all queries that retrieve nodes.

Node access query alter will then check to see if a
user can see the nodes in the result.

(http://druptest7.dev:8888/example_tag)

What about the others?
! db_update, db_insert,
db_delete
!   Similar syntax
!   Assemble and execute.

db_insert
!   Syntax: $query = db_insert('node', $options);
$nid = db_insert('node')
->fields(array(
'title' => ’This Example',
'uid' => 1,
'created' => REQUEST_TIME,
))
->execute();
db_insert returns the auto-increment value defined by
hook_schema.

(http://druptest7.dev:8888/example_insert)

db_update
$num_updated = db_update('node')
->fields(array(
'uid' => 1
))
->condition('uid', 2)
->execute();

db_update returns the number of records updated.

http://druptest7.dev:8888/example_update

db_delete
Signature: $query = db_delete('node', $options);

$num_deleted = db_delete('node')
->condition('nid', 5)
->execute();

db_delete returns the number of rows deleted.

http://druptest7.dev:8888/example_delete

db_select extenders
!   Extenders - implements a decorator pattern, currently only 2
! 
TableSort and PagerQuery = adds the methods for these
extension to query

!   example:
$query = $query
->extend('TableSort')
->orderByHeader($header);

!   Put these near the start.
!   Not chainable, if you forget to return it to itself it will have odd
results.

http://druptest7.dev:8888/example_extend

TIME FOR BONUS ROUND
YUB NUB

What is the ?
Now that you have Drupal DB Chops
You may start to consider…

To VIEWS or
not to
VIEWS

DB API an Alternative to
Views
! Who will maintain the functionality?
 
! Does it require a lot of custom views code?
 
! Are you doing a lot of aggregated data work?
 
! Do you need a highly tuned SQL statement for performance?
 
! Do you need a lot of user facing, non programmer modifications,
 
will site builders be cloning views or modifying displays?
!   Are you integrating with other modules (panels, voting, etc)?
!   How complex are the changes you need to views default
queries/output?

To views or not to views (http://drupal.org/node/242311 )

Quick case study:
•  Client wanted private comments
•  Client wanted to see a listing of all comments
made against all nodes
•  Views can do this but it is described as “hacky”
•  Created a db_select with pager and table
extenders

Questions and Thank you!
David Diers, Developer
Four Kitchens
david.diers@fourkitchens.com

D.O - thebruce
@beautyhammer

Drupal - dbtng 25th Anniversary Edition

Drupal - dbtng 25th Anniversary Edition

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