十一、mongodb之字段更新运算符

柔光的暖阳◎ 2022-05-13 05:28 323阅读 0赞

\#                           字段更新运算符

<table> 
 <thead> 
  <tr> 
   <th align="center">运算符</th> 
   <th align="center">含义</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="center">$currentDate</td> 
   <td align="center">将字段的值设置为当前日期，可以是Date或Timestamp。</td> 
  </tr> 
  <tr> 
   <td align="center">$inc</td> 
   <td align="center">按指定的数量增加字段的值</td> 
  </tr> 
  <tr> 
   <td align="center">$min</td> 
   <td align="center">仅当指定的值小于现有字段值时才更新字段</td> 
  </tr> 
  <tr> 
   <td align="center">$max</td> 
   <td align="center">仅当指定的值大于现有字段值时才更新字段</td> 
  </tr> 
  <tr> 
   <td align="center">$mul</td> 
   <td align="center">将字段的值乘以指定的量</td> 
  </tr> 
  <tr> 
   <td align="center">$rename</td> 
   <td align="center">重命名字段</td> 
  </tr> 
  <tr> 
   <td align="center">$set</td> 
   <td align="center">设置文档中字段的值</td> 
  </tr> 
  <tr> 
   <td align="center">$setOnInsert</td> 
   <td align="center">如果更新导致文档插入，则设置字段的值。对修改现有文档的更新操作没有影响</td> 
  </tr> 
  <tr> 
   <td align="center">$unset</td> 
   <td align="center">从文档中删除指定的字段</td> 
  </tr> 
 </tbody> 
</table>

\#\#\#1、$currentDate当前日期运算符

例子：

{ _id: 1, status: "a", lastModified: ISODate("2013-10-02T01:11:18.965Z") }

操作：

使用$currentDate运算符对字段设为当前日期。
    
    db.users.update(
       { _id: 1 },
       {
         $currentDate: {
            lastModified: true,
            "cancellation.date": { $type: "timestamp" }
         },
         $set: {
            status: "D",
            "cancellation.reason": "user request"
         }
       }
    )

结果：

{
       "_id" : 1,
       "status" : "D",
       "lastModified" : ISODate("2014-09-17T23:25:56.314Z"),
       "cancellation" : {
          "date" : Timestamp(1410996356, 1),
          "reason" : "user request"
       }
    }

\#\#\#2、$inc增减运算符  
例子：

{
      _id: 1,
      sku: "abc123",
      quantity: 10,
      metrics: {
        orders: 2,
        ratings: 3.5
      }
    }

运算：

使用$inc运算符对字段进行增减操作
    
    db.products.update(
       { sku: "abc123" },
       { $inc: { quantity: -2, "metrics.orders": 1 } }
    )

结果:

{
       "_id" : 1,
       "sku" : "abc123",
       "quantity" : 8,
       "metrics" : {
          "orders" : 3,
          "ratings" : 3.5
       }
    }

\#\#\#3、$min保留小运算符

例子：

{ _id: 1, highScore: 800, lowScore: 200 }

运算：

$min指定值为150，150与lowScore比较，保留小的。
    
    db.scores.update( { _id: 1 }, { $min: { lowScore: 150 } } )

结果：

{ _id: 1, highScore: 800, lowScore: 150 }

\#\#\#4、$max保留大运算符

例子：

{ _id: 1, highScore: 800, lowScore: 200 }

运算：

谁大保留谁。
    
    db.scores.update( { _id: 1 }, { $max: { highScore: 950 } } )

结果：

{ _id: 1, highScore: 950, lowScore: 200 }

\#\#\#5、$mul乘法运算符

例子：

{ "_id" : 1, "item" : "ABC", "price" : NumberDecimal("10.99"), "qty" : 25 }

运算：

db.products.update(
       { _id: 1 },
       { $mul: { price: NumberDecimal("1.25"), qty: 2 } }
    )

结果：

{ "_id" : 1, "item" : "ABC", "price" : NumberDecimal("13.7375"), "qty" : 50 }

\#\#\#6、$rename重命名运算符  
例子：

{
      "_id": 1,
      "alias": [ "The American Cincinnatus", "The American Fabius" ],
      "mobile": "555-555-5555",
      "nmae": { "first" : "george", "last" : "washington" }
    }

运算：

db.students.updateMany( {}, { $rename: { "nmae": "name" } } )

结果：

{
      "_id": 1,
      "alias": [ "The American Cincinnatus", "The American Fabius" ],
      "mobile": "555-555-5555",
      "name": { "first" : "george", "last" : "washington" }
    }

\#\#\#7、$set字段设置运算符

例子：

{
      _id: 100,
      sku: "abc123",
      quantity: 250,
      instock: true,
      reorder: false,
      details: { model: "14Q2", make: "xyz" },
      tags: [ "apparel", "clothing" ],
      ratings: [ { by: "ijk", rating: 4 } ]
    }

运算：

db.products.update(
       { _id: 100 },
       { $set:
          {
            quantity: 500,
            details: { model: "14Q3", make: "xyz" },
            tags: [ "coats", "outerwear", "clothing" ]
          }
       }
    )

\#\#\#8、$setOnInsert有就设值，没有就插入

db.products.update(
      { _id: 1 },
      {
         $set: { item: "apple" },
         $setOnInsert: { defaultQty: 100 }
      },
      { upsert: true }
    )

\#\#\#9、$unset删除字段运算符

删除sku值为"unknown"的quantity、instock字段
    
    
    db.products.update(
       { sku: "unknown" },
       { $unset: { quantity: "", instock: "" } }
    )

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