比较2个字段的MongoDB查询条件？

要查询比较 2 个字段的条件，请使用以下语法 -

db.yourCollectionName.find( { $where: function() { returnthis.yourFirstFieldName<this.yourSecondFieldName} } ).pretty();

为了理解语法，让我们用文档创建一个集合。使用文档创建集合的查询如下 -

> db.comparingTwoFieldsDemo.insertOne({"StudentName":"John","StudentAge":21,"StudentMathMarks":99,"StudentPhysicsMarks":98});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c8ac09e6cea1f28b7aa0807")
}
> db.comparingTwoFieldsDemo.insertOne({"StudentName":"Carol","StudentAge":22,"StudentMathMarks":79,"StudentPhysicsMarks":89});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c8ac0b46cea1f28b7aa0808")
}
> db.comparingTwoFieldsDemo.insertOne({"StudentName":"David","StudentAge":24,"StudentMathMarks":39,"StudentPhysicsMarks":45});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c8ac0c96cea1f28b7aa0809")
}
> db.comparingTwoFieldsDemo.insertOne({"StudentName":"Bob","StudentAge":23,"StudentMathMarks":87,"StudentPhysicsMarks":78});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c8ac0e06cea1f28b7aa080a")
}

在find()方法的帮助下显示集合中的所有文档。查询如下：

> db.comparingTwoFieldsDemo.find().pretty();

以下是输出 -

{
   "_id" : ObjectId("5c8ac09e6cea1f28b7aa0807"),
   "StudentName" : "John",
   "StudentAge" : 21,
   "StudentMathMarks" : 99,
   "StudentPhysicsMarks" : 98
}
{
   "_id" : ObjectId("5c8ac0b46cea1f28b7aa0808"),
   "StudentName" : "Carol",
   "StudentAge" : 22,
   "StudentMathMarks" : 79,
   "StudentPhysicsMarks" : 89
}
{
   "_id" : ObjectId("5c8ac0c96cea1f28b7aa0809"),
   "StudentName" : "David",
   "StudentAge" : 24,
   "StudentMathMarks" : 39,
   "StudentPhysicsMarks" : 45
}
{
   "_id" : ObjectId("5c8ac0e06cea1f28b7aa080a"),
   "StudentName" : "Bob",
   "StudentAge" : 23,
   "StudentMathMarks" : 87,
   "StudentPhysicsMarks" : 78
}

这是比较 2 个字段的条件查询 -

> db.comparingTwoFieldsDemo.find( { $where: function() { returnthis.StudentMathMarks<this.StudentPhysicsMarks} } ).pretty();

以下是输出 -

{
   "_id" : ObjectId("5c8ac0b46cea1f28b7aa0808"),
   "StudentName" : "Carol",
   "StudentAge" : 22,
   "StudentMathMarks" : 79,
   "StudentPhysicsMarks" : 89
}
{
   "_id" : ObjectId("5c8ac0c96cea1f28b7aa0809"),
   "StudentName" : "David",
   "StudentAge" : 24,
   "StudentMathMarks" : 39,
   "StudentPhysicsMarks" : 45
}