Detailed explanation of YII related query

This article mainly introduces the relevant information of YII related query. Friends in need can refer to it. I hope to be helpful.

1. Configuration of multi-table correlation

Before we use AR to perform correlation queries, we need to let AR know what an AR class is related to another.

The relationship between two AR classes is directly related through the relationship between the data tables represented by the AR classes. From a database perspective, there are three types of relationships between tables A and B: one-to-many (such as tbl_user and tbl_post), one-to-one (such as tbl_user and tbl_profile) and many-to-many Many (many-to-many such as tbl_category and tbl_post). In AR, there are four relationships:

BELONGS_TO (belongs to): If the relationship between tables A and B is one-to-many, then table B belongs to table A (for example, Post belongs to User);

HAS_MANY (there are multiple): If the relationship between tables A and B is one-to-many, then A has multiple Bs (for example, User has multiple Posts);

HAS_ONE (there is one) : This is a special case of HAS_MANY. A can have at most one B (for example, User can have at most one Profile);

MANY_MANY: This corresponds to the many-to-many relationship in the database. Since most DBMS do not directly support many-to-many relationships, a relationship table is needed to split the many-to-many relationship into a one-to-many relationship. In our example data structure, tbl_post_category is used for this purpose. In AR terms, we can interpret MANY_MANY as the combination of BELONGS_TO and HAS_MANY. For example, Post belongs to many (belongs to many) Category, and Category has many (has many). The relationship defined in Post.

AR needs to override the relations() method in CActiveRecord. This method returns an array of relationship configurations. Each array element represents a single relationship in the following format.

'VarName'=>array('RelationType', 'ClassName', 'ForeignKey', ...additional options)

Some points that need to be clarified:

1) models/Post.php

class Post extends CActiveRecord 
{ 
...... 
public function relations() 
{ 
return array( 
'author'=>array(self::BELONGS_TO, 'User', 'author_id'), 
); 
} 
}

(2)models/User.php

class User extends CActiveRecord 
{ 
...... 
public function relations() 
{ 
return array( 
'posts'=>array(self::HAS_MANY, 'Post', 'author_id'), 
'profile'=>array(self::HAS_ONE, 'Profile', 'owner_id'), 
); 
} 
}

Example 2, many-to-many relationship

'Users' => array(self::MANY_MANY, 'User', 'fail_parts_user(fail_parts_id, user_id)'),

In User.php

'FailParts' => array(self::MANY_MANY, 'FailParts', 'fail_parts_user(user_id, fail_parts_id)'),

Example 3, one-to-one relationship

VarName is basically the same as B. But not necessarily exactly the same. At this time, you can access B and its attribute values ​​​​through VarName in A's views/A/xx.php.

If it is many-to-one: author_name = $post->Author->name;
If it is one-to-many: $posts = $author->Post;
If it is many-to-many: $posts = $author->Post;//The essence is to split it into one-to-many and many-to-one

foreach($posts as $u){ 
$_tmp_titles[] = $u -> title; 
} 
titleStr = implode(', ', $_tmp_titles);

## 2. The use of multi-table associations is often used in In controllers

(1)many-to-one

$post = Post::model()->findByPk (10);

Note: The essence here is one-to-one.

(2) One-to-many

$user = User::model()->findByPk(10);

(3) Many-to-many

It is important to note that the two IDs have a sequential relationship.

From the perspective of the $repairInfo instance, the relationship must be

'FailParts' => array(self::MANY_MANY, 'FailParts', 'repair_mapping(repair_info_id,fail_parts_id)'),

From the perspective of the $failParts instance angle, the association becomes

'RepairInfos' => array(self::MANY_MANY, 'RepairInfo', 'repair_mapping(fail_parts_id, repair_info_id)'),

而前面也已经指出，不需要双方都配置，只需需要的一方设置即可。

之前曾使用过的笨方法：

/*方法一：使用表关系（多对多）*/ 
$fails = $repairInfo->FailParts;//在$repairInfo中使用 
/*方法二：使用原始方法*/ 
$id = $repairInfo->id; 
$maps = RepairMapping::model()->findAll("repair_info_id = $id"); 
$f_ids = array(); 
foreach($maps as $map){ 
array_push($f_ids, $maps[0]->fail_parts_id); 
} 
$f_idsStr = implode(',',$f_ids); 
$fails = FailParts::model()->findAll("id IN ($f_idsStr)");

2，主动加载——with

（1）一对多
（2）多对多

$posts = Post::model()->('author')->findAll();

例子：

User.php

//查询一个机房$idc_id的所有用户 
function getAdminedUsersByIdc($idc_id){ 
$c = new CDbCriteria(); 
$c->join = "JOIN idc_user on t.id=idc_user.user_id"; 
$c->condition = "idc_user.idc_id=$idc_id"; 
return User::model()->with('Idcs')->findAll($c); 
} 
//规则中配置 
'Idcs' => array(self::MANY_MANY, 'Idc', 'idc_user(user_id, idc_id)'),

批注：没有with('Idcs')，执行后的结果也一样。只不过不再是eager loading。

三、带参数的关联配置

常见的条件有

1，condition 按某个表的某个字段加过滤条件

例如：

//在User的model里定义，如下关联关系 
'doingOutsources' => array(self::MANY_MANY, 'Outsource', 'outsource_user(user_id, outsource_id)', 
'condition' => "doingOutsources.status_id IN(" . Status::ASSIGNED . "," . Status::STARTED ."," . Status::REJECTED .")"),

//结论：condition是array里指定model的一个字段。

显然，doingOutsources是真实数据表Outsource的别名，所以在condition中可以使用doingOutsources.status_id，当然也可以使用Outsource.status_id。另本表名user的默认别名是t。

2，order 按某个表的某个字段升序或降序

//在RepairInfo的model里定义，如下关联关系 
'WorkSheet' => array(self::HAS_MANY, 'WorkSheet', 'repair_info_id', order => 'created_at desc'), 
//调用 
$worksheets = $repair_info->WorkSheet; //此时$worksheets是按降序排列

//结论：order是array里指定model的一个字段。

with
joinType
select
params
on
alias
together
group
having
index

还有用于lazy loading的
limit 只取5个或10个
offset
through
官方手册
'posts'=>array(self::HAS_MANY， 'post', 'author_id', 'order'=>'posts.create_time DESC', 'with'=>'categories'),

四、静态查询（仅用于HAS_MANY和MANY_MANY）

关键字：self:STAT

1，基本用法。例如，

class Post extends CActiveRecord 
{ 
...... 

public function relations() 
{ 
return array( 
'commentCount'=>array(self::STAT, 'Comment', 'post_id'), 
'categoryCount'=>array(self::STAT,'Category','post_category(post_id, category_id)'); 

); 
} 
}

2，静态查询也支持上面的各种条件查询
如

'doingOutsourceCount' => array(self::STAT, 'Outsource', 'outsource_user(user_id, outsource_id)', 
'condition' => "outsource.status_id IN(" . Status::ASSIGNED . "," . Status::STARTED ."," . Status::REJECTED .")"),

其他查询还包括

condition 使用较多

order
select
defaultValue
params
group
having

3，静态查询的加载方式

可以使用lazy loading方式
$post->commentCount.
也可以使用eager loading方式
$posts = Post::model()->with('commentCount','categoryCount')->findAll();
注with中字符串一定是别名。

两者的性能比较：

如果需要取所有post的所有comment，前者需要2N+1次查询，而后者只有一次。两者的选择视情况而定。

相关推荐：

Yii2中的代码自动加载机制

Yii框架中的form表单

Yii2实现增删改查后留在当前页的方法详解

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