如何在mongoDB ..中編寫連接查詢？

Question

該mysql查詢的mongoDB查詢如何在mongoDB中使用join存在我正面臨在mysql中編寫的問題？

SELECT t.uid, count(j.job_id) AS x 
FROM verify AS t 
LEFT JOIN jobs AS j 
ON t.uid = j.job_id 

Answer 1

這就像下面通過使用聚合框架與$project & $lookup管道：

db.collection1.aggregation[{ 
    $project: { 

     'uid': 1, 
     "x": { 
      "$size": "job_id" 
     } 
    }, 

    $lookup: { 
     from: 'collection2', 
     localField: 'uid', 
     foreignField: 'job_id', 
     as: 'j' 
    } 
}]