YII2中查询生成器Query()的使用

YII2中的yii\db\Query给我们提供了非常丰富的方法，方便我们构建复杂的SQL语句。

Query()与createCommand最大区别在于，后者直接使用我们写好的SQL语句，前者通过参数和数据库类型生成不同SQL，迁移性更好。

<?php

namespace app\controllers;

use YII;
use yii\db\Query;
use yii\web\Controller;

class TestController extends Controller
{
    public function actionTest()
    {
        //YII2的Query的使用
        //Query与createCommand的区别是createCommand是直接写一个SQL来执行。
        //Query是根据参数和数据库类型生成不同的SQL，提升数据库可迁移性。

        //通过all查询多条记录
        //我这里用tb_user表来进行演示
        $data1 = (new Query())->select(['id','name'])
            ->from('{{%user}}')
            ->all();

        //指定where条件查询
        $data2 = (new Query())->select(['id','name'])
            ->from('{{%user}}')
            ->where('id=:id',[':id' => '2'])
            ->all();

        //通过one查询单条记录
        $data3 = (new Query())->select(['id','name'])
            ->from('{{%user}}')
            ->where('id=3')
            ->one();

        //判断记录是否存在
        $exists = (new Query())->from('{{%user}}')
            ->where('name="aaa"')
            ->exists();

        if ($exists) {
            echo 'name=aaa 存在';
        }

        //定义字段别名
        //注意真实的字段名写后面，别名写前面
        $data4 = (new Query())->select(['ids' => 'id','names' => 'name'])
            ->from('{{%user}}')
            ->where('1=1')
            ->all();

        //通过orderby排序，和limit限制条数
        $data5 = (new Query())->select(['id','name'])
            ->from('{{%user}}')
            ->where('1=1')
            ->orderBy('id desc')
            ->limit(3)
            ->all();

        //多个and条件
        //参数是数组，一个key对应一个value，默认以and拼接
        $data6 = (new Query())->select(['id','name'])
            ->from('{{%user}}')
            ->where(['id' => 3,'name' => 'aaa'])
            ->one();

        //in条件
        $data7 = (new Query())->select(['id','name'])
            ->from('{{%user}}')
            ->where(['id' => [4,5,6]])
            ->all();

        //或者如下方式
        $data7_2 = (new Query())->select(['id','name'])
            ->from('{{%user}}')
            ->where(['in','id',[4,6]])
            ->all();

        //count统计
        $count = (new Query())->from('{{%user}}')->count();
        echo '总记录数: ',$count;

        //大于，大于等于，小于，小于等于where条件
        $data8 = (new Query())->select(['id','name'])
            ->from('{{%user}}')
            ->where(['>=',5])
            ->all();

        $data9 = (new Query())->select(['id','name'])
            ->from('{{%user}}')
            ->where(['<=',3])
            ->all();

        //like查询
        $data10 = (new Query())->select(['id','name'])
            ->from('{{%user}}')
            ->where(['like','name','dd'])
            ->all();

        //between筛选和group by分组
        //查找出age在18到24之间的，并按sex分组
        $data11 = (new Query())->select(['id','name'])
            ->from('{{%user}}')
            ->where(['between','age',18,24])
            ->groupBy('sex')
            ->all();

        //having筛选
        //按sex分组，然后统计人数大于3的
        $data12 = (new Query())->select(['sex','cnt' => 'count(*)'])
            ->from('{{%user}}')
            ->groupBy('sex')
            ->having('cnt > 3')
            ->all();

        //or逻辑条件
        //查找姓名为aaa或bbb的用户
        //之前where数组是以key=>value方式传递的，如果要表达复杂逻辑关系，
        //数组第一个元素必须声明是什么逻辑，and还是or
        //第二个元素表示逻辑左边
        //第三个元素表示逻辑右边
        $data13 = (new Query())->select(['id','name'])
            ->from('{{%user}}')
            ->where(['or',['name' => 'aaa'],['name' => 'bbb']])
            ->all();

        //复杂的where条件
        //我这里只是作为演示
        //SELECT `id`,`name` FROM `tb_user` WHERE ((`name`='aaa') OR (`name`='bbb')) OR ((`name`='ccc') OR (`name`='ddd'))
        $data14 = (new Query())->select(['id','name'])
            ->from('{{%user}}')
            ->where([
                'or',[
                    'or',['name' => 'bbb'],],['name' => 'ccc'],['name' => 'ddd'],])
            ->all();

        //and和or嵌套where条件
        //SELECT `id`,`name` FROM `tb_user` WHERE (`sex`=1) AND ((`name` LIKE '%aa%') OR (`name` LIKE '%bb%'))
        $data15 = (new Query())->select(['id','name'])
            ->from('{{%user}}')
            ->where([
                'and',['sex' => 1],['like','aa'],'bb'],])
            ->all();

        //有些时候我们需要根据用户传递过来的参数追加where条件
        //追加and条件
        $query = (new Query())->select(['id','name'])
            ->from('{{%user}}')
            ->where('sex=1');
        //追加age大于18的条件
        $query->andWhere(['>',18]);
        echo $query->createCommand()->getRawSql();

        //追加or条件
        $query2 = (new Query())->select(['id','aa']);
        //追加name相似bb的条件
        $query2->orWhere(['like','bb']);
        echo $query2->createCommand()->getRawSql();

        //表别名和连接查询
        //SELECT `u`.`id`,`u`.`name`,`aa`.`item_name` FROM `tb_user` `u` LEFT JOIN `tb_auth_assignment` `aa` ON aa.user_id = u.id
        $data16 = (new Query())->select(['u.id','u.name','aa.item_name'])
            ->from(['u' => '{{%user}}'])
            ->leftJoin(['aa' => '{{%auth_assignment}}'],'aa.user_id = u.id')
            ->all();
    }
}