Data Types数据类型

Equality and Sort Order相等和排序顺序

Values of the Decimal128 type are compared and sorted with other numeric types based on their actual numeric value. Decimal128类型的值根据其实际数值与其他数值类型进行比较和排序。Numeric values of the binary-based Double type generally have approximate representations of decimal-based values and may not be exactly equal to their decimal representations.基于二进制的Double类型的数值通常具有基于十进制的值的近似表示，并且可能不完全等于它们的十进制表示。

Return Date as a String返回日期为字符串

To return the date as a string, use the Date() method, as in the following example:要以字符串形式返回日期，请使用date()方法，如下例所示：

var myDateString = Date();

To print the value of the variable, type the variable name in the shell, as in the following:要打印变量的值，请在shell中键入变量名，如下所示：

myDateString

The result is the value of myDateString:结果是myDateString的值：

Wed Dec 19 2012 01:03:25 GMT-0500 (EST)

To verify the type, use the typeof operator, as in the following:要验证类型，请使用typeof运算符，如下所示：

typeof myDateString

The operation returns string.该操作返回string。

Return Date返回日期

mongosh wraps objects of Date type with the ISODate helper; however, the objects remain of type Date.mongosh使用ISODate辅助程序包装Date类型的对象；但是，对象仍然是Date类型。

The following example uses both the new Date() constructor and the ISODate() constructor to return Date objects.以下示例同时使用new Date()构造函数和ISODate()构造器来返回Date对象。

var myDate = new Date();
var myDateInitUsingISODateWrapper = ISODate();

You can use the new operator with the ISODate() constructor as well.您也可以将new运算符与ISODate()构造函数一起使用。

To print the value of the variable, type the variable name in the shell, as in the following:要打印变量的值，请在shell中键入变量名，如下所示：

myDate

The result is the Date value of myDate wrapped in the ISODate() helper:结果是包裹在ISODate()帮助程序中的myDate的Date值：

ISODate("2012-12-19T06:01:17.171Z")

To verify the type:要验证类型，请执行以下操作：

var myDate = ISODate("2021-03-21T06:00:00.171Z")
Object.prototype.toString.call(myDate) === "[object Date]"

The operation returns true.操作返回true。

Numeric Types数值类型

Consider the types collection:考虑types集合：

{ _id: 1, value: 1, expectedType: 'Int32' },
{ _id: 2, value: Long("1"), expectedType: 'Long' },
{ _id: 3, value: 1.01, expectedType: 'Double' },
{ _id: 4, value: Decimal128("1.01"), expectedType: 'Decimal128' },
{ _id: 5, value: 3200000001, expectedType: 'Double' }

This table shows the results of the db.types.find( <QUERY> ) command for the corresponding <QUERY>. The type names and aliases are given on the BSON types page.此表显示了相应<QUERY>的db.types.find( <QUERY> )命令的结果。类型名称和别名在BSON类型页面上给出。

{
   "value":
      {
         $type: "int"
      }
}

{
   _id: 1,
   value: 1,
   expectedType: 'Int32'
}

{
   "value":
      {
         $type: "long"
      }
}

{
   _id: 2,
   value: Long("1"),
   expectedType: 'Long'
}

{
   "value":
      {
         $type: "decimal"
      }
}

{
   _id: 4,
   value: Decimal128("1"),
   expectedType: 'Decimal128'
}

{
   "value":
      {
         $type: "double"
      }
}

{
   _id: 3,
   value: 1.01,
   expectedType: 'Double'
}
{
   _id: 5,
   value: 3200000001,
   expectedType: 'Double'
}

{
   "value":
      {
         $type: "number"
      }
}

{
    _id: 1,
    value: 1,
    expectedType: 'Int32'
}
{
    _id: 2,
    value: Long("1"),
    expectedType: 'Long'
}
{
    _id: 3,
    value: 1.01,
    expectedType: 'Double'
}
{
    _id: 4,
    value: Decimal128("1.01"),
    expectedType: 'Decimal128'
}
{
    _id: 5,
    value: 3200000001,
    expectedType: 'Double'
}

{
    "value": 1.01
}

{
    _id: 3,
    value: 1.01,
    expectedType: 'Double'
}

{
    "value": 1
}

{
    _id: 1,
    value: 1,
    expectedType: 'Int32'
}
{
    _id: 2,
    value: Long("1"),
    expectedType: 'Long'
}

The query { "value": 1.01 } implicitly searches for the Double representation of 1.01. Document _id: 4 is a Decimal128 so it is not selected.查询{ "value": 1.01 }隐式搜索1.01的Double表示。文档_id: 4是Decimal128，因此未被选中。

Note, however, that { "value": 1 } returns both Int32 and Long types.但是请注意，{ "value": 1 }同时返回Int32和Long类型。

Default Numeric Type Consistency默认数字类型一致性

Consider the typeExample collection. This collection consists of two identical documents, { "a": 1 }. 考虑typeExample集合。此集合由两个相同的文档组成，{ "a": 1 }。The first document was created in the legacy mongo shell, the second document was created in mongosh.第一个文档是在遗留的mongo shell中创建的，第二个文档是用mongosh创建的。

We can use the $type operator in an aggregation pipeline to see the type that was assigned in each shell.我们可以在聚合管道中使用$type运算符来查看在每个shell中分配的类型。

db.typeExample.aggregate(
  [
    {
       $project:
         {
           "valueType":
             {
               "$type": "$a"
             },
           "_id": 0
         }
    }
  ]
)

In the first document, created in the legacy mongo shell, the value was stored as a double. In the mongosh document the value was stored as type int.在第一个在遗留mongo shell中创建的文档中，该值被存储为double。在mongosh文档中，该值存储为int类型。

[
  {
     valueType: 'double'  // inserted in legacy mongo shell
  },
  {
     valueType: 'int'     // inserted in mongosh
  }
]

Timestamp a New Document为新文档添加时间戳

Use Timestamp() without parameters to insert multiple documents using the default settings:使用不带参数的Timestamp()使用默认设置插入多个文档：

db.flights.insertMany(
   [
      { arrival: "true", ts: Timestamp() },
      { arrival: "true", ts: Timestamp() },
      { arrival: "true", ts: Timestamp() }
   ]
)

Run db.flights.find({}) to see the timestamps. Notice that even though all three entries were stamped in the same second, the interval was incremented on each one.运行db.flights.find({})查看时间戳。请注意，即使所有三个条目都在同一秒内盖章，间隔也会在每个条目上递增。

[
   {
      _id: ObjectId("6114216907d84f5370391919"),
      arrival: 'true',
      ts: Timestamp({ t: 1628709225, i: 1 })
   },
   {
      _id: ObjectId("6114216907d84f537039191a"),
      arrival: 'true',
      ts: Timestamp({ t: 1628709225, i: 2 })
   },
   {
      _id: ObjectId("6114216907d84f537039191b"),
      arrival: 'true',
      ts: Timestamp({ t: 1628709225, i: 3 })
   }
]

Create a Custom Timestamp创建自定义时间戳

Use custom parameters to insert multiple documents with a specific Timestamp.使用自定义参数插入具有特定Timestamp的多个文档。

This operation inserts three documents into the flights collection and uses the UNIX epoch value 1627811580 to set the ts times to 9:53 GMT on August 1, 2021.此操作将三个文档插入到flights（航班）集合中，并使用UNIX纪元值1627811580将ts时间设置为2021年8月1日格林尼治标准时间9:53。

db.flights.insertMany(
   [
      { arrival: "true", ts: Timestamp(1627811580, 10) },
      { arrival: "true", ts: Timestamp(1627811580, 20) },
      { arrival: "true", ts: Timestamp(1627811580, 30) }
   ]
)

The resulting documents look like this:生成的文档如下：

[
   {
      _id: ObjectId("6123d8315e6bba6f61a1031c"),
      arrival: 'true',
      ts: Timestamp({ t: 1627811580, i: 10 })
   },
   {
      _id: ObjectId("6123d8315e6bba6f61a1031d"),
      arrival: 'true',
      ts: Timestamp({ t: 1627811580, i: 20 })
   },
   {
      _id: ObjectId("6123d8315e6bba6f61a1031e"),
      arrival: 'true',
      ts: Timestamp({ t: 1627811580, i: 30 })
   }
]

Type Checking with $type()使用$Type()进行类型检查

The $type query operator accepts either a string alias or a numeric code corresponding to the data type. $type查询运算符接受与数据类型对应的字符串别名或数字代码。See BSON Types for a list of BSON data types and their corresponding numeric codes.有关BSON数据类型及其相应数字代码的列表，请参阅BSON类型。

For example, these checks for the Decimal128 type are equivalent:例如，Decimal128类型的这些检查是等效的：

db.types.find( { "value": { $type: "decimal" } } )
db.types.find( { "value": { $type: 19 } } )

Type Checking with a Constructor与构造函数进行类型检查

Examine the object constructor to determine the type. For example, the output of db.collection.find() is a Cursor.检查对象constructor以确定类型。例如，db.collection.find()的输出是一个Cursor（游标）。

var findResults = db.housing.find({"multiUnit": true} )
findResults.constructor.name     // Returns the type返回其类型