$lte

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Definition定义

$lte

Syntax: 语法：{ field: { $lte: value } }

$lte selects the documents where the value of the field is less than or equal to (i.e. <=) the specified value.选择field值小于或等于（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

Consider the following example:考虑以下示例：

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

This query will select all documents in the inventory collection where the quantity field value is less than or equal to 20.此查询将选择inventory集合中quantity字段值小于或等于20的所有单据。

Example output:示例输出：

{
  _id: ObjectId("61ba453ffe687fce2f04241c"),
  item: 'washers',
  quantity: 10,
  carrier: { name: 'Shipit', fee: 1 }
}

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 $lte comparison against a field in an embedded document.以下示例基于$lte与嵌入文档中的字段的比较来设置price字段。

db.inventory.updateMany(
   { "carrier.fee": { $lte: 5 } }, { $set: { price: 9.99 } }
)

Example output:示例输出：

{
  _id: ObjectId("61ba453ffe687fce2f04241a"),
  item: 'nuts',
  quantity: 30,
  carrier: { name: 'Shipit', fee: 3 },
  price: 9.99
},
{
  _id: ObjectId("61ba453ffe687fce2f04241b"),
  item: 'bolts',
  quantity: 50,
  carrier: { name: 'Shipit', fee: 4 },
  price: 9.99
},
{
  _id: ObjectId("61ba453ffe687fce2f04241c"),
  item: 'washers',
  quantity: 10,
  carrier: { name: 'Shipit', fee: 1 },
  price: 9.99
}

This updateMany() operation searches for an embedded document, carrier, with a subfield named fee. 此updateMany()操作搜索嵌入的文档carrier，其子字段名为fee。It sets { price: 9.99 } in each document where fee has a value less than or equal to 5.它在每个fee值小于或等于5的文档中设置{price:9.99}。

To set the value of the price field in only the first document where carrier.fee is less than or equal to 5, use updateOne().要仅在carrier.fee小于或等于5的第一个文档中设置price字段的值，请使用updateOne()。

Tip提示
See also: 参阅：
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