$ne
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Definition定义
$ne-
Syntax:
{ field: { $ne: value } }$neselects the documents where the value of the选择fieldis not equal to the specifiedvalue.field值不等于指定值的文档。This includes documents that do not contain the这包括不包含该field.field的文档。For comparison of different BSON type values, see the specified BSON comparison order.有关不同BSON类型值的比较，请参阅指定的BSON比较顺序。
Examples实例
The following examples use the 以下示例使用inventory collection. Create the collection:inventory集合。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 选择inventory collection where quantity is not equal to 20:inventory集合中quantity不等于20的所有单据：
db.inventory.find( { quantity: { $ne: 20 } } )
The query will also select documents that do not have the 查询还将选择没有quantity field.quantity字段的文档。
Example output:示例输出：
{
_id: ObjectId("61ba667dfe687fce2f042420"),
item: 'nuts',
quantity: 30,
carrier: { name: 'Shipit', fee: 3 }
},
{
_id: ObjectId("61ba667dfe687fce2f042421"),
item: 'bolts',
quantity: 50,
carrier: { name: 'Shipit', fee: 4 }
},
{
_id: ObjectId("61ba667dfe687fce2f042422"),
item: 'washers',
quantity: 10,
carrier: { name: 'Shipit', fee: 1 }
}
Perform an Update Based on Embedded Document Fields基于嵌入的文档字段执行更新
The following example sets the 以下示例根据price field based on a $ne comparison against a field in an embedded document.$ne与嵌入文档中某个字段的比较设置price字段。
db.inventory.updateMany( { "carrier.fee": { $ne: 1 } }, { $set: { "price": 9.99 } } )
Example output:输出示例：
{
_id: ObjectId("61ba66e2fe687fce2f042423"),
item: 'nuts',
quantity: 30,
carrier: { name: 'Shipit', fee: 3 },
price: 9.99
},
{
_id: ObjectId("61ba66e2fe687fce2f042424"),
item: 'bolts',
quantity: 50,
carrier: { name: 'Shipit', fee: 4 },
price: 9.99
},
{
_id: ObjectId("61ba66e2fe687fce2f042425"),
item: 'washers',
quantity: 10,
carrier: { name: 'Shipit', fee: 1 }
}
This 此updateMany() operation searches for an embedded document, carrier, with a subfield named fee. updateMany()操作搜索带有一个名为fee的子字段的嵌入文档carrier。It sets 它在每个{ price: 9.99 } in each document where fee has a value that does not equal 1 or where the fee subfield does not exist.fee值不等于1或不存在fee子字段的文档中设置{price:9.99}。
The inequality operator 不等式运算符$ne is not very selective since it often matches a large portion of the index. $ne不是很有选择性，因为它经常匹配索引的很大一部分。As a result, in many cases, a 因此，在许多情况下，带有索引的$ne query with an index may perform no better than a $ne query that must scan all documents in a collection. $ne查询的性能可能并不比必须扫描集合中所有文档的$ne搜索好。See also Query Selectivity.另请参见查询选择性。