$type

Arrays数组

For documents where field is an array, $type returns documents in which at least one array element matches a type passed to $type.对于field为数组的文档，$type返回至少有一个数组元素与传递给$type的类型匹配的文档。

Querying for the Array BSON Type查询数组BSON类型

With MongoDB 3.6 and later, querying for $type: "array" returns documents where the field itself is an array. 对于MongoDB3.6及更高版本，查询$type: "array"将返回字段本身是数组的文档。Prior to MongoDB 3.6, $type: "array" returned documents where the field is an array containing at least one element of type array. 在MongoDB3.6之前，$type: "array"返回的文档中，字段是一个至少包含一个array类型元素的数组。For example, given the following documents:例如，给定以下文档：

{ "data" : [ "values", [ "values" ] ] }
{ "data" : [ "values" ] }

With MongoDB 3.6 and later, the query find( {"data" : { $type : "array" } } ) returns both documents. 对于MongoDB3.6及更高版本，查询find( {"data" : { $type : "array" } } )返回两个文档。Prior to MongoDB 3.6, the query returns only the first document.在MongoDB 3.6之前，查询只返回第一个文档。

Available Types可用类型

Starting in MongoDB 3.2, $type operator accepts string aliases for the BSON types in addition to the numbers corresponding to the BSON types. 从MongoDB3.2开始，$type运算符除了接受BSON类型对应的数字外，还接受BSON类的字符串别名。Previous versions only accepted the numbers corresponding to the BSON type. 以前的版本只接受与BSON类型对应的编号。[1]

$type supports the number alias, which will match against the following BSON types:支持number别名，该别名将与以下BSON类型匹配：

• double
• 32-bit integer
• 64-bit integer
• decimal

For examples, see Examples.有关示例，请参阅示例。

MinKey and MaxKeyMinKey和MaxKey

MinKey and MaxKey are used in comparison operations and exist primarily for internal use. MinKey和MaxKey用于比较操作，主要供内部使用。For all possible BSON element values, MinKey will always be the smallest value while MaxKey will always be the greatest value.对于所有可能的BSON元素值，MinKey总是最小值，而MaxKey总是最大值。

Querying for minKey or maxKey with $type will only return fields that match the special MinKey or MaxKey values.使用$type查询minKey或maxKey将只返回与特殊minKey或maxKey值匹配的字段。

Suppose that the data collection has two documents with MinKey and MaxKey:假设data集合有两个带有MinKey和MaxKey的文档：

{ "_id" : 1, x : { "$minKey" : 1 } }
{ "_id" : 2, y : { "$maxKey" : 1 } }

The following query will return the document with _id: 1:以下查询将返回带有_id:1的文档：

db.data.find( { x: { $type: "minKey" } } )

The following query will return the document with _id: 2:以下查询将返回带有_id:2的文档：

db.data.find( { y: { $type: "maxKey" } } )

Querying by Data Type按数据类型查询

The addressBook contains addresses and zipcodes, where zipCode has string, int, double, and long values:addressBook包含地址和邮政编码，其中zipCode有string、int、double和long值：

db.addressBook.insertMany(
   [
      { "_id" : 1, address : "2030 Martian Way", zipCode : "90698345" },
      { "_id" : 2, address: "156 Lunar Place", zipCode : 43339374 },
      { "_id" : 3, address : "2324 Pluto Place", zipCode: NumberLong(3921412) },
      { "_id" : 4, address : "55 Saturn Ring" , zipCode : NumberInt(88602117) },
      { "_id" : 5, address : "104 Venus Drive", zipCode : ["834847278", "1893289032"]}
   ]
)

The following queries return all documents where zipCode is the BSON type string or is an array containing an element of the specified type:以下查询返回所有文档，其中zipCode是BSON类型string或是包含指定类型元素的数组：

db.addressBook.find( { "zipCode" : { $type : 2 } } );
db.addressBook.find( { "zipCode" : { $type : "string" } } );

These queries return:这些查询返回：

{ "_id" : 1, "address" : "2030 Martian Way", "zipCode" : "90698345" }
{ "_id" : 5, "address" : "104 Venus Drive", "zipCode" : [ "834847278", "1893289032" ] }

The following queries return all documents where zipCode is the BSON type double or is an array containing an element of the specified type:以下查询返回所有文档，其中zipCode是BSON类型的double或是包含指定类型元素的数组：

db.addressBook.find( { "zipCode" : { $type : 1 } } )
db.addressBook.find( { "zipCode" : { $type : "double" } } )

These queries return:这些查询返回：

{ "_id" : 2, "address" : "156 Lunar Place", "zipCode" : 43339374 }

The following query uses the number alias to return documents where zipCode is the BSON type double, int, or longor is an array containing an element of the specified types:以下查询使用number别名返回文档，其中zipCode是BSON类型double、int或long或是包含指定类型元素的数组：

db.addressBook.find( { "zipCode" : { $type : "number" } } )

These queries return:这些查询返回：

{ "_id" : 2, "address" : "156 Lunar Place", "zipCode" : 43339374 }
{ "_id" : 3, "address" : "2324 Pluto Place", "zipCode" : NumberLong(3921412) }
{ "_id" : 4, "address" : "55 Saturn Ring", "zipCode" : 88602117 }

Querying by Multiple Data Type按多数据类型查询

The grades collection contains names and averages, where classAverage has string, int, and double values:grades集合包含名称和平均值，其中classAverage具有string、int和double值：

db.grades.insertMany(
   [
      { "_id" : 1, name : "Alice King" , classAverage : 87.333333333333333 },
      { "_id" : 2, name : "Bob Jenkins", classAverage : "83.52" },
      { "_id" : 3, name : "Cathy Hart", classAverage: "94.06" },
      { "_id" : 4, name : "Drew Williams" , classAverage : NumberInt("93") }
   ]
)

The following queries return all documents where classAverage is the BSON type string or double or is an array containing an element of the specified types. 以下查询返回classAverage是BSON类型string或double或是包含指定类型元素的数组的所有文档。The first query uses numeric aliases while the second query uses string aliases.第一个查询使用数字别名，而第二个查询使用字符串别名。

db.grades.find( { "classAverage" : { $type : [ 2 , 1 ] } } );
db.grades.find( { "classAverage" : { $type : [ "string" , "double" ] } } );

These queries return the following documents:这些查询返回以下文档：

{ "_id" : 1, "name" : "Alice King", "classAverage" : 87.33333333333333 }
{ "_id" : 2, "name" : "Bob Jenkins", "classAverage" : "83.52" }
{ "_id" : 3, "name" : "Cathy Hart", "classAverage" : "94.06" }

Querying by MinKey and MaxKey按MinKey和MaxKey查询

The restaurants collection uses minKey for any grade that is a failing grade:restaurants集合对任何不及格的等级使用minKey：

{
   "_id": 1,
   "address": {
      "building": "230",
      "coord": [ -73.996089, 40.675018 ],
      "street": "Huntington St",
      "zipcode": "11231"
   },
   "borough": "Brooklyn",
   "cuisine": "Bakery",
   "grades": [
      { "date": new Date(1393804800000), "grade": "C", "score": 15 },
      { "date": new Date(1378857600000), "grade": "C", "score": 16 },
      { "date": new Date(1358985600000), "grade": MinKey(), "score": 30 },
      { "date": new Date(1322006400000), "grade": "C", "score": 15 }
   ],
   "name": "Dirty Dan's Donuts",
   "restaurant_id": "30075445"
}

And maxKey for any grade that is the highest passing grade:最高及格等级的任何等级的maxKey：

{
   "_id": 2,
   "address": {
      "building": "1166",
      "coord": [ -73.955184, 40.738589 ],
      "street": "Manhattan Ave",
      "zipcode": "11222"
   },
   "borough": "Brooklyn",
   "cuisine": "Bakery",
   "grades": [
      { "date": new Date(1393804800000), "grade": MaxKey(), "score": 2 },
      { "date": new Date(1378857600000), "grade": "B", "score": 6 },
      { "date": new Date(1358985600000), "grade": MaxKey(), "score": 3 },
      { "date": new Date(1322006400000), "grade": "B", "score": 5 }
   ],
   "name": "Dainty Daisey's Donuts",
   "restaurant_id": "30075449"
}

The following query returns any restaurant whose grades.grade field contains minKey or is an array containing an element of the specified type:以下查询返回grades.grade字段包含minKey或是包含指定类型元素的数组的任何餐厅：

db.restaurants.find(
   { "grades.grade" : { $type : "minKey" } }
)

This returns这将返回

{
   "_id" : 1,
   "address" : {
      "building" : "230",
      "coord" : [ -73.996089, 40.675018 ],
      "street" : "Huntington St",
      "zipcode" : "11231"
   },
   "borough" : "Brooklyn",
   "cuisine" : "Bakery",
   "grades" : [
      { "date" : ISODate("2014-03-03T00:00:00Z"), "grade" : "C", "score" : 15 },
      { "date" : ISODate("2013-09-11T00:00:00Z"), "grade" : "C", "score" : 16 },
      { "date" : ISODate("2013-01-24T00:00:00Z"), "grade" : { "$minKey" : 1 }, "score" : 30 },
      { "date" : ISODate("2011-11-23T00:00:00Z"), "grade" : "C", "score" : 15 }
   ],
   "name" : "Dirty Dan's Donuts",
   "restaurant_id" : "30075445"
}

The following query returns any restaurant whose grades.grade field contains maxKey or is an array containing an element of the specified type:以下查询返回grades.grade字段包含maxKey或是包含指定类型元素的数组的任何餐厅：

db.restaurants.find(
   { "grades.grade" : { $type : "maxKey" } }
)

This returns这将返回

{
   "_id" : 2,
   "address" : {
      "building" : "1166",
      "coord" : [ -73.955184, 40.738589 ],
      "street" : "Manhattan Ave",
      "zipcode" : "11222"
   },
   "borough" : "Brooklyn",
   "cuisine" : "Bakery",
   "grades" : [
      { "date" : ISODate("2014-03-03T00:00:00Z"), "grade" : { "$maxKey" : 1 }, "score" : 2 },
      { "date" : ISODate("2013-09-11T00:00:00Z"), "grade" : "B", "score" : 6 },
      { "date" : ISODate("2013-01-24T00:00:00Z"), "grade" : { "$maxKey" : 1 }, "score" : 3 },
      { "date" : ISODate("2011-11-23T00:00:00Z"), "grade" : "B", "score" : 5 }
   ],
   "name" : "Dainty Daisey's Donuts",
   "restaurant_id" : "30075449"
}