require,require_dependency,extend,include

extend vs include
* extend - class level
* include - instance level

require vs require_dependency
require_dependency wiki

require 是 ruby 的, require_dependency 是rails 的, 在development mode 時, 每個request 都會在load 一下

join,include

mysql, 是沒有include 這種東西的
在rails 下join 如
<br />#用join 就會把所有的relation table 全都join 起來變成大table<br />AdFile.find(:all, :joins => :locations)<br /><br />SELECT `ad_files`.* FROM `ad_files` INNER JOIN `file_locations` ON (`ad_files`.`id` = `file_locations`.`ad_file_id`) INNER JOIN `locations` ON (`locations`.`id` = `file_locations`.`location_id`)<br /><br />#如果是用include 意義是一樣, 可是rails 會幫妳把他分成幾個sql 去做, 這樣就不會因為join 的table 太大會痛了<br />AdFile.find(:all, :include => :locations)<br /><br /> SELECT * FROM `ad_files` <br /> SELECT `file_locations`.* FROM `file_locations` WHERE (`file_locations`.ad_file_id IN (17,18,19))<br /> SELECT * FROM `locations` WHERE (`locations`.`id` IN (1,2,3)) <br />
rails 用join 就是用inner join 弄成一整個大的object, association 就沒了
用include 有的時候因為條件裡直接需要用到另個table 的條件, 是用left join 但仍維持 association 的關係
<br />AdFile.find(:all, :joins => :locations, :conditions => {:locations => {:code => 'goyou_top'}}).first.locations<br /><br />SELECT `ad_files`.`id` AS t0_r0, `ad_files`.`buyer_id` AS t0_r1, `ad_files`.`render_num` AS t0_r2, `ad_files`.`file_type` AS t0_r3, `ad_files`.`filename` AS t0_r4, `ad_files`.`redirect_url` AS t0_r5, `ad_files`.`start_at` AS t0_r6, `ad_files`.`expire_at` AS t0_r7, `ad_files`.`created_at` AS t0_r8, `ad_files`.`active` AS t0_r9, `locations`.`id` AS t1_r0, `locations`.`code` AS t1_r1, `locations`.`height` AS t1_r2, `locations`.`width` AS t1_r3 FROM `ad_files` LEFT OUTER JOIN `file_locations` ON (`ad_files`.`id` = `file_locations`.`ad_file_id`) LEFT OUTER JOIN `locations` ON (`locations`.`id` = `file_locations`.`location_id`) WHERE (locations.code = 'goyou_top')<br />#如果妳就算不取locations 會發現sql 也一樣<br /><br /><br />AdFile.find(:all, :joins => :locations, :conditions => {:locations => {:code => 'goyou_top'}}).first.locations<br /><br /> SELECT `ad_files`.* FROM `ad_files` INNER JOIN `file_locations` ON (`ad_files`.`id` = `file_locations`.`ad_file_id`) INNER JOIN `locations` ON (`locations`.`id` = `file_locations`.`location_id`) WHERE (`locations`.`code` = 'goyou_top')<br /><br />SELECT `locations`.* FROM `locations` INNER JOIN file_locations ON locations.id = file_locations.location_id WHERE ((`file_locations`.ad_file_id = 18))<br />#會發現location 根本是重新在join 一次去取的<br />#但其實要取location 的資料可以直接在join 回來的object 直接拿就可以了<br />

另外rails 2.2 可以把 join 寫的high 一點了
Easy Join Table Conditions<br />class Article < ActiveRecord::Base<br /> belongs_to :user<br />end<br /><br />class User < ActiveRecord::Base<br /> has_many :articles<br />end<br /><br /># Get all the users that have published articles<br />User.find(:all, :joins => :article,<br /> :conditions => ["articles.published = ?", true])<br /><br /># high 一點的寫法<br /># Get all the users that have published articles <br />User.find(:all, :joins => :article,<br /> :conditions => { :articles => { :published => true } })<br />

join,include

mysql, 是沒有include 這種東西的
在rails 下join 如
<br />#用join 就會把所有的relation table 全都join 起來變成大table<br />AdFile.find(:all, :joins => :locations)<br /><br />SELECT `ad_files`.* FROM `ad_files` INNER JOIN `file_locations` ON (`ad_files`.`id` = `file_locations`.`ad_file_id`) INNER JOIN `locations` ON (`locations`.`id` = `file_locations`.`location_id`)<br /><br />#如果是用include 意義是一樣, 可是rails 會幫妳把他分成幾個sql 去做, 這樣就不會因為join 的table 太大會痛了<br />AdFile.find(:all, :include => :locations)<br /><br /> SELECT * FROM `ad_files` <br /> SELECT `file_locations`.* FROM `file_locations` WHERE (`file_locations`.ad_file_id IN (17,18,19))<br /> SELECT * FROM `locations` WHERE (`locations`.`id` IN (1,2,3)) <br />
rails 用join 就是用inner join 弄成一整個大的object, association 就沒了
用include 有的時候因為條件裡直接需要用到另個table 的條件, 是用left join 但仍維持 association 的關係
<br />AdFile.find(:all, :joins => :locations, :conditions => {:locations => {:code => 'goyou_top'}}).first.locations<br /><br />SELECT `ad_files`.`id` AS t0_r0, `ad_files`.`buyer_id` AS t0_r1, `ad_files`.`render_num` AS t0_r2, `ad_files`.`file_type` AS t0_r3, `ad_files`.`filename` AS t0_r4, `ad_files`.`redirect_url` AS t0_r5, `ad_files`.`start_at` AS t0_r6, `ad_files`.`expire_at` AS t0_r7, `ad_files`.`created_at` AS t0_r8, `ad_files`.`active` AS t0_r9, `locations`.`id` AS t1_r0, `locations`.`code` AS t1_r1, `locations`.`height` AS t1_r2, `locations`.`width` AS t1_r3 FROM `ad_files` LEFT OUTER JOIN `file_locations` ON (`ad_files`.`id` = `file_locations`.`ad_file_id`) LEFT OUTER JOIN `locations` ON (`locations`.`id` = `file_locations`.`location_id`) WHERE (locations.code = 'goyou_top')<br />#如果妳就算不取locations 會發現sql 也一樣<br /><br /><br />AdFile.find(:all, :joins => :locations, :conditions => {:locations => {:code => 'goyou_top'}}).first.locations<br /><br /> SELECT `ad_files`.* FROM `ad_files` INNER JOIN `file_locations` ON (`ad_files`.`id` = `file_locations`.`ad_file_id`) INNER JOIN `locations` ON (`locations`.`id` = `file_locations`.`location_id`) WHERE (`locations`.`code` = 'goyou_top')<br /><br />SELECT `locations`.* FROM `locations` INNER JOIN file_locations ON locations.id = file_locations.location_id WHERE ((`file_locations`.ad_file_id = 18))<br />#會發現location 根本是重新在join 一次去取的<br />#但其實要取location 的資料可以直接在join 回來的object 直接拿就可以了<br />

另外rails 2.2 可以把 join 寫的high 一點了
Easy Join Table Conditions<br />class Article < ActiveRecord::Base<br /> belongs_to :user<br />end<br /><br />class User < ActiveRecord::Base<br /> has_many :articles<br />end<br /><br /># Get all the users that have published articles<br />User.find(:all, :joins => :article,<br /> :conditions => ["articles.published = ?", true])<br /><br /># high 一點的寫法<br /># Get all the users that have published articles <br />User.find(:all, :joins => :article,<br /> :conditions => { :articles => { :published => true } })<br />

include, map

user 拿全部的x_alerts

[model]
  belongs_to :user
  has_many :x_alerts, :extend => XAlert::AssociationMethods, :through => :x_alert_relationships
  has_many :x_alert_relationships


 a = u.alert_targets.find(:all, :include => {:x_alert_relationships => :x_alert} )

   AlertTarget Load (0.000180)   SELECT * FROM `alert_targets` WHERE (`alert_targets`.user_id = 2590)
  XAlertRelationship Load (0.000152)   SELECT `x_alert_relationships`.* FROM `x_alert_relationships` WHERE (`x_alert_relationships`.alert_target_id IN (1,2,10,11))
  XAlert Load (0.000212)   SELECT * FROM `x_alerts` WHERE (`x_alerts`.id IN ('6','216','7','8','250','229','218','241','197','214','104','5'))

a.map  {|e| xar = e.x_alert_relationships; xar.map { |k| h = k.x_alert; h[:cat] = k.created_at; h}}.flatten

model, include, left outer join

>>User.find(:all, :include => 'profile')
  User Load (0.000682)   SELECT * FROM `users`
  Profile Load (0.000492)   SELECT `profiles`.* FROM `profiles` WHERE (`profiles`.user_id IN (1,2,4,5))
  Profile Columns (0.000880)   SHOW FIELDS FROM `profiles`


>> User.find(:all, :include => 'profile', :conditions => "users.name is not NULL")
  User Load (0.000731)   SELECT * FROM `users` WHERE (users.name is not NULL)
  Profile Load (0.000183)   SELECT `profiles`.* FROM `profiles` WHERE (`profiles`.user_id IN (1,2,4,5))


User.find(:all, :include => 'profile', :conditions => "profiles.others is NULL")
  User Load Including Associations (0.001349)   SELECT `users`.`id` AS t0_r0, `users`.`name` AS t0_r1, `users`.
`password_salt` AS t0_r2, `users`.`password_hash` AS t0_r3, `users`.`email` AS t0_r4, `users`.`created_at` AS t
0_r5, `users`.`cookie_hash` AS t0_r6, `users`.`target_time_now` AS t0_r7, `users`.`reset_password_code` AS t0_r
8, `users`.`reset_password_code_until` AS t0_r9, `users`.`yahoo_userhash` AS t0_r10, `users`.`group_id` AS t0_r
11, `users`.`group_nickname` AS t0_r12, `users`.`time_zone` AS t0_r13, `profiles`.`id` AS t1_r0, `profiles`.`user_id` AS t1_r1, `profiles`.`others` AS t1_r2, `profiles`.`sex` AS t1_r3, `profiles`.`birth` AS t1_r4, `profiles`.`star` AS t1_r5, `profiles`.`blood` AS t1_r6, `profiles`.`address` AS t1_r7, `profiles`.`school` AS t1_r8, `profiles`.`job` AS t1_r9, `profiles`.`interest` AS t1_r10, `profiles`.`photo` AS t1_r11, `profiles`.`connect` AS t1_r12, `profiles`.`email_weekly` AS t1_r13 FROM `users` LEFT OUTER JOIN `profiles` ON profiles.user_id = users.id WHERE (profiles.others is NULL)