如何通过MongoDB中的两个键删除重复项？
要通过两个键删除重复的条目，请在MongoDB中使用Aggregate()。让我们创建一个包含文档的集合-
> db.demo108.insertOne({"Value1":23,"Value2":24});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e2ee3e49fd5fd66da214477")
}
> db.demo108.insertOne({"Value1":23,"Value2":25});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e2ee3f29fd5fd66da214478")
}
> db.demo108.insertOne({"Value1":23,"Value2":24});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e2ee3f59fd5fd66da214479")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo108.find();
这将产生以下输出-
{ "_id" : ObjectId("5e2ee3e49fd5fd66da214477"), "Value1" : 23, "Value2" : 24 }
{ "_id" : ObjectId("5e2ee3f29fd5fd66da214478"), "Value1" : 23, "Value2" : 25 }
{ "_id" : ObjectId("5e2ee3f59fd5fd66da214479"), "Value1" : 23, "Value2" : 24 }以下是通过MongoDB中的两个键删除重复条目的查询-
> db.demo108.aggregate([{ "$sort": { "_id": 1 } },
... {
... "$group": {
... "_id": { "Value1": "$Value1", "Value2": "$Value2" },
... "doc": { "$first": "$$ROOT" }
... }
... },
... { "$replaceRoot": { "newRoot": "$doc" } },
... { "$out": "demo108" }]);在find()方法的帮助下显示集合中的所有文档-
> db.demo108.find();
这将产生以下输出-
{ "_id" : ObjectId("5e2ee3f29fd5fd66da214478"), "Value1" : 23, "Value2" : 25 }
{ "_id" : ObjectId("5e2ee3e49fd5fd66da214477"), "Value1" : 23, "Value2" : 24 }