$gt
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Definition定义
$gt-
Syntax:
{ field: { $gt: value } }$gtselects those documents where the value of the选择fieldis greater than (i.e.>) the specifiedvalue.field值大于（即>）指定值的文档。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，比较运算符只对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通过类型支架支持有限的跨BSON比较。
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 greater than 20:inventory集合中quantity大于20的所有单据：
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 $gt comparison against a field in an embedded document.$gt与嵌入文档中某个字段的比较设置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 此updateOne() operation searches for an embedded document, carrier, with a subfield named fee. updateOne()操作搜索带有一个名为fee的子字段的嵌入文档carrier。It sets 它在找到的第一个文档中设置{ price: 9.99 } in the first document it finds where fee has a value greater than 2.{ price: 9.99 }，其中fee的值大于2。
To set the value of the 要在price field in all documents where carrier.fee is greater than 2, use updateMany().carrier.fee大于2的所有文档中设置价格字段的值，请使用updateMany()。