MongoDb php的聚合函數問題

我是mongoDb的新手，在使用聚合函數時遇到問題。我試圖得到字段「期望」和「總體」的總和，但它返回0.我也想在同一個查詢中使用非空或空的註釋的總數。MongoDb php的聚合函數問題

$out = $collection->aggregate 
(
    array(   
     array('$match' => array('id' => 6200)), 
      array ('$unwind' => '$reviews'), 
       array('$group' => array('_id' => '$id', 
        'exptotal' => array('$sum' => array('reviews' => '$expectations')),     
        'total' => array('$sum' => array('reviews' => '$overall')),     
        'count' => array('$sum' => 1) 
        ) 
      ) 
     ) 

);

這裏是JSON

{ 
"_id": "528c62406a542f7c6a6bf522", 
"id": 6200, 
"categories": [ 
    { 
     "id": 6, 
     "name": "Artificial Intelligence" 
    }, 
    { 
     "id": 5, 
     "name": "Statistics and Data Analysis" 
    } 
], 
"courseId": "COURSE_16", 
"institute": { 
    "id": 5693, 
    "name": "YZ University" 
}, 
"instructors": [ 
    " A Morris" 
], 
"language": "en", 
"reviews": [ 
    { 
     "username": "kalis", 
     "expectations": 3, 
     "content": 2, 
     "overall": 3, 
     "comments": "This is really good course for improvement", 
     "datecreated": "2013-11-02T17:04:11.102Z" 
    }, 
    { 
     "username": "julia", 
     "expectations": 4, 
     "content": 2, 
     "overall": 2, 
     "comments": "This improves my skill a lot", 
     "datecreated": "2013-11-03T17:04:11.102Z" 
    }, 
    { 
     "username": "john", 
     "expectations": 2, 
     "content": 4, 
     "overall": 4, 
     "comments": "", 
     "datecreated": "2013-11-04T17:04:11.102Z" 
    } 
], 
"shortName": "ml", 
"title": "Machine Learning"

}

來源

2013-11-22 Mark Green

這看起來像它的工作：

$out = $collection->aggregate(array(
    array('$match' => array('id' => 6200)), 
    array ('$unwind' => '$reviews'), 
    array('$unwind' => '$comments'), 
    array('$group' => array('_id' => '$id', 
     'commTotal' => array('$sum' => array('$cond'=>array(array('$eq'=>array('$comments',null),0,1)))), 
     'exptotal' => array('$sum' => '$reviews.expectations'), 
     'total' => array('$sum' => '$reviews.overall'), 
     'count' => array('$sum' => 1) 
    )) 
));

的原因是，當你$unwind數據仍處於子文檔字段只是該子文檔已成爲單個審閱的對象。

該文檔對這個操作符有點誤導，我會給你。

來源

2013-11-22 08:09:41 Sammaye

感謝它完美的工作！另外，如果我想要在同一個查詢中使用非空或空的評論總數，該怎麼辦？ –

@MarkGreen你可以做兩件事，你的樣品不會顯示評論欄，所以我有點猜測，但是如果你做兩次展開，它會有效地解開你的兩個朋友，然後你應該能夠總結出兩個部分。 – Sammaye

@MarkGreen增加了一些樣本 – Sammaye

MongoDb php的聚合函數問題

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