Detailed explanation of addition, deletion, modification and query of Yii2.0 database operations

1. Simple query:

]: 根据查询结果返回查询的第一条记录。

[[all()]]: 根据查询结果返回所有记录。

[[count()]]: 返回记录的数量。

[[sum()]]: 返回指定列的总数。

[[average()]]: 返回指定列的平均值。

[[min()]]: 返回指定列的最小值。

[[max()]]: 返回指定列的最大值。

[[scalar()]]: 返回查询结果的第一行中的第一列的值。

[[column()]]: 返回查询结果中的第一列的值。

[[exists()]]: 返回一个值，该值指示查询结果是否有数据。

[[where()]]: 添加查询条件

[[with()]]: 该查询应执行的关系列表。

[[indexBy()]]: 根据索引的列的名称查询结果。

[[asArray()]]: 以数组的形式返回每条记录。

[code=php]Customer::find()->one();    此方法返回一条数据；

Customer::find()->all();    此方法返回所有数据；

Customer::find()->count();    此方法返回记录的数量；

Customer::find()->average();    此方法返回指定列的平均值；

Customer::find()->min();    此方法返回指定列的最小值 ；

Customer::find()->max();    此方法返回指定列的最大值 ；

Customer::find()->scalar();    此方法返回值的第一行第一列的查询结果；

Customer::find()->column();    此方法返回查询结果中的第一列的值；

Customer::find()->exists();    此方法返回一个值指示是否包含查询结果的数据行；

Customer::find()->asArray()->one();    以数组形式返回一条数据；  
  
Customer::find()->asArray()->all();    以数组形式返回所有数据；

Customer::find()->where($condition)->asArray()->one();    根据条件以数组形式返回一条数据；  
  
Customer::find()->where($condition)->asArray()->all();    根据条件以数组形式返回所有数据；

Customer::find()->where($condition)->asArray()->orderBy('id DESC')->all();    根据条件以数组形式返回所有数据,并根据ID倒序；

2. Related query:

[[ActiveRecord::hasOne()]]：返回对应关系的单条记录
[[ActiveRecord::hasMany()]]：返回对应关系的多条记录[/code]

Application example:

);
    }
     
    public function getCountry()
    {
        //客户和国家是一对一的关系所以用hasOne
        return $this->hasOne(CountrysModel::className(), ['id'=>'Country_id']);
    }
    ....
}
      
// 查询客户与他们的订单和国家
CustomerModel::find()->with('orders', 'country')->all();

// 查询客户与他们的订单和订单的发货地址
CustomerModel::find()->with('orders.address')->all();

// 查询客户与他们的国家和状态为1的订单
CustomerModel::find()->with([
    'orders' => function ($query) {
        $query->andWhere('status = 1');
        },
        'country',
])->all();

：with中的orders对应getOrders

<b>常见问题：</b>

1.在查询时加了->select();如下，要加上order_id，即关联的字段（比如：order_id）比如要在select中，否则会报错：undefined index order_id

// 查询客户与他们的订单和国家
CustomerModel::find()->select(&#39;order_id&#39;)->with(&#39;orders&#39;, &#39;country&#39;)->all();

)->one();  
// 查询年龄为30，状态值为1的客户  
$customer = Customer::findOne(['age' => 30, 'status' => 1]);  
$customer = Customer::find()->where(['age' => 30, 'status' => 1])->one();  
// 查询key值为10的所有客户  
$customers = Customer::findAll(10);  
$customers = Customer::find()->where(['id' => 10])->all();  
// 查询key值为10，11,12的客户  
$customers = Customer::findAll([10, 11, 12]);  
$customers = Customer::find()->where(['id' => [10, 11, 12]])->all();  
// 查询年龄为30，状态值为1的所有客户  
$customers = Customer::findAll(['age' => 30, 'status' => 1]);  
$customers = Customer::find()->where(['age' => 30, 'status' => 1])->all();  
  
<b>where()条件：</b>  
  
$customers = Customer::find()->where($cond)->all();   
  
$cond写法举例：  
  
// SQL: (type = 1) AND (status = 2).  
$cond = [&#39;type&#39; => 1, &#39;status&#39; => 2]   
  
// SQL:(id IN (1, 2, 3)) AND (status = 2)  
$cond = [&#39;id&#39; => [1, 2, 3], &#39;status&#39; => 2]   
  
//SQL:status IS NULL  
$cond = [&#39;status&#39; => null]  
  
<b>[[]]</b>:将不同的条件组合在一起，用法举例：  
  
//SQL:`id=1 AND id=2`  
$cond = [&#39;and&#39;, &#39;id=1&#39;, &#39;id=2&#39;]  
  
//SQL:`type=1 AND (id=1 OR id=2)`  
$cond = [&#39;and&#39;, &#39;type=1&#39;, [&#39;or&#39;, &#39;id=1&#39;, &#39;id=2&#39;]]

[[or]]:

], ['id' => [1, 2, 3]]  
  
<b>[[]]:</b>  
  
//SQL:`NOT (attribute IS NULL)`  
$cond = [&#39;not&#39;, [&#39;attribute&#39; => null]]

[[between]]: not between Same usage

<b>[[]]: </b>not in 用法类似  
  
//SQL:`id IN (1, 2, 3)`  
$cond = [&#39;in&#39;, &#39;id&#39;, [1, 2, 3]]  
  
//IN条件也适用于多字段  
$cond = [&#39;in&#39;, [&#39;id&#39;, &#39;name&#39;], [[&#39;id&#39; => 1, &#39;name&#39; => &#39;foo&#39;], [&#39;id&#39; => 2, &#39;name&#39; => &#39;bar&#39;]]]  
  
//也适用于内嵌sql语句  
$cond = [&#39;in&#39;, &#39;user_id&#39;, (new Query())->select(&#39;id&#39;)->from(&#39;users&#39;)->where([&#39;active&#39; => 1])]

[[like]]:

//SQL:`name LIKE '%test%' AND name LIKE '%sample%'`  
$cond = ['like', 'name', ['test', 'sample']]  
  
//SQL:`name LIKE '%tester'`  
$cond = ['like', 'name', '%tester', false]  
  
<b>[[]]: </b>not exists用法类似  
  
//SQL:EXISTS (SELECT "id" FROM "users" WHERE "active"=1)  
$cond = [&#39;exists&#39;, (new Query())->select(&#39;id&#39;)->from(&#39;users&#39;)->where([&#39;active&#39; => 1])]

Also, you can specify any operator as follows

//SQL:`id >= 10`
$cond = ['>=', 'id', 10]

//SQL:`id != 10`
$cond = ['!=', 'id', 10]

Commonly used Query:

// WHERE admin_id >= 10 LIMIT 0,10
User::find()->select('*')->where(['>=', 'admin_id', 10])->offset(0)->limit(10)->all()
// SELECT `id`, (SELECT COUNT(*) FROM `user`) AS `count` FROM `post` 
 $subQuery = (new Query())->select('COUNT(*)')->from('user'); 
 $query = (new Query())->select(['id', 'count' => $subQuery])->from('post');
// SELECT DISTINCT `user_id` ... 
User::find()->select('user_id')->distinct();

Update:

//update();
//runValidation boolen 是否通过validate()校验字段 默认为true 
//attributeNames array 需要更新的字段 
$model->update($runValidation , $attributeNames); 

//updateAll();
//update customer set status = 1 where status = 2
Customer::updateAll(['status' => 1], 'status = 2'); 

//update customer set status = 1 where status = 2 and uid = 1;
Customer::updateAll(['status' => 1], ['status'=> '2','uid'=>'1']);

Delete:

$model = Customer::findOne($id);
$model->delete();

$model->deleteAll(['id'=>1]);

Batch insert:

Yii::$app->db->createCommand()->batchInsert(UserModel::tableName(), ['user_id','username'], [
['1','test1'],
['2','test2'],
['3','test3'], 
])->execute();

View execution sql

//UserModel 
$query = UserModel::find()->where(['status'=>1]); 
echo $query->createCommand()->getRawSql();

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