$ne (aggregation)（聚合）

Definition定义

$ne

Compares two values and returns:比较两个值并返回：

• true when the values are not equivalent.当值不相等时为true。
• false when the values are equivalent.当值相等时为false。

The $ne compares both value and type, using the specified BSON comparison order for values of different types.$ne使用指定的BSON比较顺序对不同类型的值进行值和类型比较。

$ne has the following syntax:具有以下语法：

{ $ne: [ <expression1>, <expression2> ] }

For more information on expressions, see Expressions.有关表达式的详细信息，请参阅表达式。

Example示例

Consider an inventory collection with the following documents:考虑使用以下文件进行inventory集合：

db.inventory.insertMany( [
   { _id: 1, item: "abc1", description: "product 1", qty: 300 }
   { _id: 2, item: "abc2", description: "product 2", qty: 200 }
   { _id: 3, item: "xyz1", description: "product 3", qty: 250 }
   { _id: 4, item: "VWZ1", description: "product 4", qty: 300 }
   { _id: 5, item: "VWZ2", description: "product 5", qty: 180 }
] )

The following operation uses the $ne operator to determine if qty does not equal 250:以下操作使用$ne运算符来确定qty是否不等于250：

db.inventory.aggregate(
   [
     {
       $project:
          {
            item: 1,
            qty: 1,
            qtyNe250: { $ne: [ "$qty", 250 ] },
            _id: 0
          }
     }
   ]
)

The operation returns the following results:该操作返回以下结果：

{ item: "abc1", qty: 300, qtyNe250: true }
{ item: "abc2", qty: 200, qtyNe250: true }
{ item: "xyz1", qty: 250, qtyNe250: false }
{ item: "VWZ1", qty: 300, qtyNe250: true }
{ item: "VWZ2", qty: 180, qtyNe250: true }