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适用对象：
MongoDB vCore
运算符 $type 返回表达式中指定的值的类型。
语法
运算符的 $type 语法为：
{ "$type": <expression> }
参数
| 参数 | DESCRIPTION |
|---|---|
expression |
要检索其类型的指定值 |
例子
请查看 StoreData 数据库中 stores 集合的这个示例文档。
{
"_id": "0fcc0bf0-ed18-4ab8-b558-9848e18058f4",
"name": "First Up Consultants | Beverage Shop - Satterfieldmouth",
"location": {
"lat": -89.2384,
"lon": -46.4012
},
"staff": {
"totalStaff": {
"fullTime": 8,
"partTime": 20
}
},
"sales": {
"totalSales": 75670,
"salesByCategory": [
{
"categoryName": "Wine Accessories",
"totalSales": 34440
},
{
"categoryName": "Bitters",
"totalSales": 39496
},
{
"categoryName": "Rum",
"totalSales": 1734
}
]
},
"promotionEvents": [
{
"eventName": "Unbeatable Bargain Bash",
"promotionalDates": {
"startDate": {
"Year": 2024,
"Month": 6,
"Day": 23
},
"endDate": {
"Year": 2024,
"Month": 7,
"Day": 2
}
},
"discounts": [
{
"categoryName": "Whiskey",
"discountPercentage": 7
},
{
"categoryName": "Bitters",
"discountPercentage": 15
},
{
"categoryName": "Brandy",
"discountPercentage": 8
},
{
"categoryName": "Sports Drinks",
"discountPercentage": 22
},
{
"categoryName": "Vodka",
"discountPercentage": 19
}
]
},
{
"eventName": "Steal of a Deal Days",
"promotionalDates": {
"startDate": {
"Year": 2024,
"Month": 9,
"Day": 21
},
"endDate": {
"Year": 2024,
"Month": 9,
"Day": 29
}
},
"discounts": [
{
"categoryName": "Organic Wine",
"discountPercentage": 19
},
{
"categoryName": "White Wine",
"discountPercentage": 20
},
{
"categoryName": "Sparkling Wine",
"discountPercentage": 19
},
{
"categoryName": "Whiskey",
"discountPercentage": 17
},
{
"categoryName": "Vodka",
"discountPercentage": 23
}
]
}
]
}
示例 1：获取 Double 值的类型
db.stores.aggregate([
{
"$match": {
"_id": "b0107631-9370-4acd-aafa-8ac3511e623d"
}
},
{
"$project": {
"longitude": "$location.lon",
"longitudeType": {
"$type": "$location.lon"
}
}
}])
此查询返回以下结果：
{
"_id": "b0107631-9370-4acd-aafa-8ac3511e623d",
"longitude": 72.8377,
"longitudeType": "double"
}
示例 2：获取字符串值的类型
db.stores.aggregate([
{
"$match": {
"_id": "b0107631-9370-4acd-aafa-8ac3511e623d"
}
},
{
"$project": {
"name": "$name",
"nameType": {
"$type": "$name"
}
}
}])
此查询返回以下结果：
{
"_id": "b0107631-9370-4acd-aafa-8ac3511e623d",
"name": "Wide World Importers | Furniture Bargains - Roobport",
"nameType": "string"
}
示例 3：获取 Int 值的类型
db.stores.aggregate([
{
"$match": {
"_id": "b0107631-9370-4acd-aafa-8ac3511e623d"
}
},
{
"$project": {
"fullTimeStaff": "$staff.totalStaff.fullTime",
"fullTimeStaffType": {
"$type": "$staff.totalStaff.fullTime"
}
}
}])
此查询返回以下结果：
{
"_id": "b0107631-9370-4acd-aafa-8ac3511e623d",
"fullTimeStaff": 3,
"fullTimeStaffType": "int"
}