$gt

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Definition定义

$gt

Syntax: 语法：{ field: { $gt: value } }

$gt selects those documents where the value of the field is greater than (i.e. >) the specified value.选择field值大于（即>）指定value的文档。

For most data types, comparison operators only perform comparisons on fields where the BSON type matches the query value's type. 对于大多数数据类型，比较运算符仅对BSON类型与查询值类型匹配的字段执行比较。MongoDB supports limited cross-BSON comparison through Type Bracketing.MongoDB通过类型括号支持有限的跨BSON比较。

Examples示例

The following examples use the inventory collection. 以下示例使用inventory集合。Create the collection:创建集合：

db.inventory.insertMany( [
   {
      "item": "nuts", "quantity": 30,
      "carrier": { "name": "Shipit", "fee": 3 }
   },
   {
      "item": "bolts", "quantity": 50,
      "carrier": { "name": "Shipit", "fee": 4 }
   },
   {
      "item": "washers", "quantity": 10,
      "carrier": { "name": "Shipit", "fee": 1 }
   }
] )

Match Document Fields匹配文档字段

Select all documents in the inventory collection where quantity is greater than 20:选择inventory集合中quantity大于20的所有文档：

db.inventory.find( { quantity: { $gt: 20 } } )

Example output:示例输出：

{
  _id: ObjectId("61ba25cbfe687fce2f042414"),
  item: 'nuts',
  quantity: 30,
  carrier: { name: 'Shipit', fee: 3 }
},
{
  _id: ObjectId("61ba25cbfe687fce2f042415"),
  item: 'bolts',
  quantity: 50,
  carrier: { name: 'Shipit', fee: 4 }
}

Perform an Update Based on Embedded Document Fields基于嵌入式文档字段执行更新

The following example sets the price field based on a $gt comparison against a field in an embedded document.以下示例基于$gt与嵌入文档中的字段的比较设置price字段。

db.inventory.updateOne(
   { "carrier.fee": { $gt: 2 } }, { $set: { "price": 9.99 } }
)

Example output:示例输出：

{
  _id: ObjectId("61ba3ec9fe687fce2f042417"),
  item: 'nuts',
  quantity: 30,
  carrier: { name: 'Shipit', fee: 3 },
  price: 9.99
},
{
  _id: ObjectId("61ba3ec9fe687fce2f042418"),
  item: 'bolts',
  quantity: 50,
  carrier: { name: 'Shipit', fee: 4 }
},
{
  _id: ObjectId("61ba3ec9fe687fce2f042419"),
  item: 'washers',
  quantity: 10,
  carrier: { name: 'Shipit', fee: 1 }
}

This updateOne() operation searches for an embedded document, carrier, with a subfield named fee. 此updateOne()操作使用名为fee的子字段搜索嵌入文档carrier。It sets { price: 9.99 } in the first document it finds where fee has a value greater than 2.它在找到的第一个文档中设置{ price: 9.99 }，其中fee的值大于2。

To set the value of the price field in all documents where carrier.fee is greater than 2, use updateMany().要在carrier.fee大于2的所有文档中设置price字段的值，请使用updateMany()。

Tip提示
See also: 参阅：
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