$each(数组更新)
适用对象: MongoDB vCore
$each
运算符在 $addToSet
或 $push
操作中使用,以便在单个更新操作中向数组字段添加多个元素。 当需要在数组中插入多个项而无需执行多个更新操作时,此运算符非常有用。 $each
运算符可确保将指定数组中的每个项添加至目标数组。
语法
{
$push: {
<field>: {
$each: [ <value1>, <value2>, ... ],
<modifier1>: <value1>,
<modifier2>: <value2>,
...
}
}
}
parameters
说明 | |
---|---|
<field> |
要更新的字段。 |
$each |
要添加至数组字段的值的数组。 |
<modifier> |
可选的修饰符,例如 $sort 、$slice 和 $position ,可控制 $push 操作的行为。 |
示例
让我们通过以下示例 json 来了解用法。
{
"_id": "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5",
"name": "Lakeshore Retail | DJ Equipment Stop - Port Cecile",
"location": {
"lat": 60.1441,
"lon": -141.5012
},
"staff": {
"totalStaff": {
"fullTime": 2,
"partTime": 0
}
},
"sales": {
"salesByCategory": [
{
"categoryName": "DJ Headphones",
"totalSales": 35921
}
],
"fullSales": 3700
},
"promotionEvents": [
{
"eventName": "Bargain Blitz Days",
"promotionalDates": {
"startDate": {
"Year": 2024,
"Month": 3,
"Day": 11
},
"endDate": {
"Year": 2024,
"Month": 2,
"Day": 18
}
},
"discounts": [
{
"categoryName": "DJ Turntables",
"discountPercentage": 18
},
{
"categoryName": "DJ Mixers",
"discountPercentage": 15
}
]
}
],
"tag": [
"#ShopLocal",
"#SeasonalSale",
"#FreeShipping",
"#MembershipDeals"
]
}
将多个新的促销活动添加至 promotionEvents
数组。
db.stores.updateOne(
{ "name": "Lenore's New DJ Equipment Store" },
{
$push: {
promotionEvents: {
$each: [
{
eventName: "Grand Savings",
promotionalDates: {
startDate: "2024-08-01",
endDate: "2024-08-31"
},
discounts: [
{
categoryName: "DJ Headphones",
discountPercentage: 5
}
]
},
{
eventName: "Big Bargain",
promotionalDates: {
startDate: "2024-11-25",
endDate: "2024-11-30"
},
discounts: [
{
categoryName: "DJ Headphones",
discountPercentage: 20
}
]
}
]
}
}
}
)
此查询将返回以下文档。
{
"acknowledged": true,
"insertedId": null,
"matchedCount": "0",
"modifiedCount": "0",
"upsertedCount": 0
}