条件查询

$customers = Customer::find()->where($cond)->all();

$cond就是我们所谓的条件，条件的写法也根据查询数据的不同存在差异，那么如何用yii2的方式来写查询条件呢？

[[简单条件]]

// SQL: (type = 1) AND (status = 2). 
$cond = ['type' => 1, 'status' => 2] 
// SQL:(id IN (1, 2, 3)) AND (status = 2) 
$cond = ['id' => [1, 2, 3], 'status' => 2] 
//SQL:status IS NULL 
$cond = ['status' => null]

【and】:将不同的条件组合在一起，用法举例：

//SQL:`id=1 AND id=2` 
$cond = ['and', 'id=1', 'id=2'] 
//SQL:`type=1 AND (id=1 OR id=2)` 
$cond = ['and', 'type=1', ['or', 'id=1', 'id=2']] 
//SQL:`type=1 AND (id=1 OR id=2)` //此写法'='可以换成其他操作符，例：in like != >=等 
$cond = [ 
 'and', 
 ['=', 'type', 1], 
 [ 
 'or', 
 ['=', 'id', '1'], 
 ['=', 'id', '2'], 
 ] 
]

[[or]]:

/SQL:`(type IN (7, 8, 9) OR (id IN (1, 2, 3)))` 
$cond = ['or', ['type' => [7, 8, 9]], ['id' => [1, 2, 3]]

[[not]]:

//SQL:`NOT (attribute IS NULL)` 
$cond = ['not', ['attribute' => null]]

[[between]]: not between 用法相同

//SQL:`id BETWEEN 1 AND 10` 
$cond = ['between', 'id', 1, 10]

[[in]]: not in 用法类似

//SQL:`id IN (1, 2, 3)` 
$cond = ['in', 'id', [1, 2, 3]] or $cond = ['id'=>[1, 2, 3]]

//IN条件也适用于多字段 
$cond = ['in', ['id', 'name'], [['id' => 1, 'name' => 'foo'], ['id' => 2, 'name' => 'bar']]] 
//也适用于内嵌sql语句 
$cond = ['in', 'user_id', (new Query())->select('id')->from('users')->where(['active' => 1])]

[[like]]:

//SQL:`name LIKE '%tester%'`
$cond = ['like', 'name', 'tester']
//SQL:`name LIKE '%test%' AND name LIKE '%sample%'`
$cond = ['like', 'name', ['test', 'sample']]
//SQL:`name LIKE '%tester'`
$cond = ['like', 'name', '%tester', false]

[[exists]]: not exists用法类似

//SQL:EXISTS (SELECT "id" FROM "users" WHERE "active"=1)
$cond = ['exists', (new Query())->select('id')->from('users')->where(['active' => 1])]

此外，您可以指定任意运算符如下：

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

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