如何在 MongoDB 的 update() 函数中递增?
mongodbdatabasebig data analytics
您可以使用 $inc 运算符来递增。我们先创建一个包含文档的集合。
> db.addInUpdateFunctionDemo.insertOne({"PlayerName":"Chris","PlayerScore":78});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd2b3f4345990cee87fd893")
}
> db.addInUpdateFunctionDemo.insertOne({"PlayerName":"Robert","PlayerScore":88});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd2b3fc345990cee87fd894")
}
> db.addInUpdateFunctionDemo.insertOne({"PlayerName":"David","PlayerScore":99});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd2b407345990cee87fd895")
}
以下是使用 find() 方法显示集合中的所有文档的查询 −
> db.addInUpdateFunctionDemo.find().pretty();
这将产生以下输出 −
{
"_id" : ObjectId("5cd2b3f4345990cee87fd893"),
"PlayerName" : "Chris",
"PlayerScore" : 78
}
{
"_id" : ObjectId("5cd2b3fc345990cee87fd894"),
"PlayerName" : "Robert",
"PlayerScore" : 88
}
{
"_id" : ObjectId("5cd2b407345990cee87fd895"),
"PlayerName" : "David",
"PlayerScore" : 99
}
以下是在 MongoDB 的 update() 函数中执行加法的查询 −
> db.addInUpdateFunctionDemo.update({_id : ObjectId("5cd2b407345990cee87fd895")},{$inc: {PlayerScore: 201}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
让我们再检查一遍所有文件
> db.addInUpdateFunctionDemo.find().pretty();
这将产生以下输出 −
{
"_id" : ObjectId("5cd2b3f4345990cee87fd893"),
"PlayerName" : "Chris",
"PlayerScore" : 78
}
{
"_id" : ObjectId("5cd2b3fc345990cee87fd894"),
"PlayerName" : "Robert",
"PlayerScore" : 88
}
{
"_id" : ObjectId("5cd2b407345990cee87fd895"),
"PlayerName" : "David",
"PlayerScore" : 300
}
