从MongoDB中的数组中提取多个对象？
要从数组中提取多个对象，可以使用$pull运算符。首先让我们创建一个包含文档的集合-
> db.pullMultipleObjectsDemo.insertOne(
... {
... "ClientId" : "100",
... "ClientName" : "John",
... "ClientPersonalDetails" : [
... {
... "ClientCountryName" : "US",
... "ClientProjectName" : "Online Book Store",
...
... },
... {
... "ClientCountryName" : "AUS",
... "ClientProjectName" : "Online Fee Management",
...
... },
... {
... "ClientCountryName" : "UK",
... "ClientProjectName" : "Online Pig Dice Game",
...
... },
... {
... "ClientCountryName" : "ANGOLA",
... "ClientProjectName" : "Online Hospital Management",
...
... }
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5cc7d0748f9e6ff3eb0ce43d")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> db.pullMultipleObjectsDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5cc7d0748f9e6ff3eb0ce43d"),
"ClientId" : "100",
"ClientName" : "John",
"ClientPersonalDetails" : [
{
"ClientCountryName" : "US",
"ClientProjectName" : "Online Book Store"
},
{
"ClientCountryName" : "AUS",
"ClientProjectName" : "Online Fee Management"
},
{
"ClientCountryName" : "UK",
"ClientProjectName" : "Online Pig Dice Game"
},
{
"ClientCountryName" : "ANGOLA",
"ClientProjectName" : "Online Hospital Management"
}
]
}以下是从数组中提取多个对象的查询-
> db.pullMultipleObjectsDemo.update(
... {"_id": ObjectId("5cc7d0748f9e6ff3eb0ce43d")},
... {"$pull":{"ClientPersonalDetails":{"ClientProjectName":{$in:["Online Book Store","Online Pig Dice Game"]}}}}
... );
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })让我们显示集合中的所有文档，以检查对象是否已从数组中删除。查询如下-
> db.pullMultipleObjectsDemo.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5cc7d0748f9e6ff3eb0ce43d"),
"ClientId" : "100",
"ClientName" : "John",
"ClientPersonalDetails" : [
{
"ClientCountryName" : "AUS",
"ClientProjectName" : "Online Fee Management"
},
{
"ClientCountryName" : "ANGOLA",
"ClientProjectName" : "Online Hospital Management"
}
]
}查看上面的示例输出，已从数组中删除了多个对象。