if else if cond in mongodb 聚合

Posted 2023-03-11

【中文标题】if else if cond in mongodb 聚合

【英文标题】：If else if cond in mongodb aggregation

【发布时间】：2019-02-25 14:31:02

【问题描述】：

我知道以前有人问过这个问题，但我似乎找不到答案，如何在聚合 $project 中添加条件

Schedul.aggregate([
     $match:  flag: 1  ,
    
        $project: 
            "name": "$name",
            "day_of_week": ("$day_of_week" === 0) ? 'Sunday' : ("$day_of_week" === 1) ? 'Monday' : ("$day_of_week" === 2) ? 'Tuesday' : ("$day_of_week" === 3) ? 'Wednesday' : ("$day_of_week" === 4) ? 'Thursday' : ("$day_of_week" === 5) ? 'Friday' : 'Saturday',
        
    ,
])

【参考方案1】：

您可以改用$switch 聚合。

Schedul.aggregate([
   "$match":  "flag": 1 ,
   "$project": 
    "name": "$name",
    "day_of_week": 
      "$switch": 
        "branches": [
           "case":  "$eq": ["$day_of_week", 0] , "then": "Sunday" ,
           "case":  "$eq": ["$day_of_week", 1] , "then": "Monday" ,
           "case":  "$eq": ["$day_of_week", 2] , "then": "Tuesday" ,
           "case":  "$eq": ["$day_of_week", 3] , "then": "Wednesday" ,
           "case":  "$eq": ["$day_of_week", 4] , "then": "Thrusday" ,
           "case":  "$eq": ["$day_of_week", 5] , "then": "Friday" 
        ],
        "default": "Saturday"
      
    
  
])