如何检查MongoDB中字段是否为数字？
要检查MongoDB中的field是否为数字，请使用$type运算符。以下是语法
db.yourCollectionName.find({youtFieldName: {$type:"number"}}).pretty();首先让我们创建一个包含文档的集合
> db.checkIfFieldIsNumberDemo.insertOne({"StudentName":"John","StudentAge":23});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9ec75dd628fa4220163b83")
}
>db.checkIfFieldIsNumberDemo.insertOne({"StudentName":"Chris","StudentMathScore":98,"StudentCountryName":"US"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9ec77cd628fa4220163b84")
}
>db.checkIfFieldIsNumberDemo.insertOne({"StudentName":"Robert","StudentCountryName":"AUS"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9ec7a4d628fa4220163b85")
}
>db.checkIfFieldIsNumberDemo.insertOne({"StudentId":101,"StudentName":"Larry","StudentCountryName":"AUS"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9ec7ccd628fa4220163b86")
}以下是在find()方法的帮助下显示集合中所有文档的查询
> db.checkIfFieldIsNumberDemo.find().pretty();
这将产生以下输出
{
"_id" : ObjectId("5c9ec75dd628fa4220163b83"),
"StudentName" : "John",
"StudentAge" : 23
}
{
"_id" : ObjectId("5c9ec77cd628fa4220163b84"),
"StudentName" : "Chris",
"StudentMathScore" : 98,
"StudentCountryName" : "US"
}
{
"_id" : ObjectId("5c9ec7a4d628fa4220163b85"),
"StudentName" : "Robert",
"StudentCountryName" : "AUS"
}
{
"_id" : ObjectId("5c9ec7ccd628fa4220163b86"),
"StudentId" : 101,
"StudentName" : "Larry",
"StudentCountryName" : "AUS"
}以下是检查字段是否为数字的查询
> db.checkIfFieldIsNumberDemo.find({StudentMathScore: {$type:"number"}}).pretty();以下是显示字段的输出，该字段是一个数字，即StudentMathScore
{
"_id" : ObjectId("5c9ec77cd628fa4220163b84"),
"StudentName" : "Chris",
"StudentMathScore" : 98,
"StudentCountryName" : "US"
}