如何更新MongoDB文档以将新项目添加到数组？
要将新项目添加到数组，可以使用$push运算符。让我们首先实现以下查询以创建包含文档的集合：
> db.updateDemo.insertOne({"StudentName":"Larry","StudentCoreSubject":["Java","C"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c98ba78330fd0aa0d2fe4c9")
}
>db.updateDemo.insertOne({"StudentName":"Robert","StudentCoreSubject":["C++","MongoDB"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c98ba8b330fd0aa0d2fe4ca")
}
> db.updateDemo.insertOne({"StudentName":"Chris","StudentCoreSubject":["Python"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c98ba9b330fd0aa0d2fe4cb")
}以下是在find()方法的帮助下显示集合中所有文档的查询
> db.updateDemo.find().pretty();
这将产生以下输出
{
"_id" : ObjectId("5c98ba78330fd0aa0d2fe4c9"),
"StudentName" : "Larry",
"StudentCoreSubject" : [
"Java",
"C"
]
}
{
"_id" : ObjectId("5c98ba8b330fd0aa0d2fe4ca"),
"StudentName" : "Robert",
"StudentCoreSubject" : [
"C++",
"MongoDB"
]
}
{
"_id" : ObjectId("5c98ba9b330fd0aa0d2fe4cb"),
"StudentName" : "Chris",
"StudentCoreSubject" : [
"Python"
]
}以下是将新项目添加到数组的查询
> db.updateDemo.update( { _id:ObjectId("5c98ba78330fd0aa0d2fe4c9") }, { $push: { "StudentCoreSubject": "MySQL" } });
Updated 1 existing record(s) in 2ms
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })现在检查项目是否插入到数组中
> db.updateDemo.find().pretty();
这将产生以下输出。字符串“MySQL”已成功插入ID5c98ba78330fd0aa0d2fe4c9
{
"_id" : ObjectId("5c98ba78330fd0aa0d2fe4c9"),
"StudentName" : "Larry",
"StudentCoreSubject" : [
"Java",
"C",
"MySQL"
]
}
{
"_id" : ObjectId("5c98ba8b330fd0aa0d2fe4ca"),
"StudentName" : "Robert",
"StudentCoreSubject" : [
"C++",
"MongoDB"
]
}
{
"_id" : ObjectId("5c98ba9b330fd0aa0d2fe4cb"),
"StudentName" : "Chris",
"StudentCoreSubject" : [
"Python"
]
}