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其十进制表示。

Return Date as a String字符串形式的返回日期

To return the date as a string, use the Date() method, as in the following example:要将日期作为字符串返回，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 返回Date

mongosh wraps objects of Date type with the ISODate helper; however, the objects remain of type Date.mongosh使用ISODate辅助对象包装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:结果是包装在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:请考虑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>. 此表显示了相应的<QUERY>的db.types.find( <QUERY> )命令的结果。The type names and aliases are given on the BSON types page.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，因此未选中它。

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. 请考虑typeExample集合。This collection consists of two identical documents, { "a": 1 }. 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mongoshell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. 在遗留mongoshell中创建的第一个文档中，该值存储为double。In the mongosh document the value was stored as type int.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()可以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. 运行db.flights.find({})查看时间戳。Notice that even though all three entries were stamped in the same second, the interval was incremented on each one.请注意，尽管所有三个条目都在同一秒内盖章，但每个条目的间隔都会增加。

[
   {
      _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.使用自定义参数可以插入具有特定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flights集合，并使用UNIX epoch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:生成的文档如下所示：

[
   {
      _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使用构造函数进行类型检查

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

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