MongoDB 简介 - 记录和值

2019-01-10 08:00:00 · 飞浪

在本指南中，我们将介绍 MongoDB 以及如何开始使用它。在本系列指南结束时，您将了解所有内容，直至基本的 CRUD（创建、检索、更新、删除）操作。今天就学习吧！

开始设置

请阅读本系列的第一个指南，以获取有关设置 MongoDB 的更多信息 -安装、Shell 和数据库管理。

批量插入

是的，你没看错。与 MySQL 一样，你也可以在一个时间点插入多条记录。同样的insert()函数不仅接受对象，还接受数组作为输入。这次，我们将偷懒，为接下来的两条记录创建一些简单的东西。

      db.students.insert([
  {
    name: "Purushothaman",
    degree: "Management",
    email: "purush@example.com"
  },
  {
    name: "Meaow Meaow",
    degree: "Cat Study",
    email: "meaow@example.com",
    phone: ["9850420420"]
  }
]);
    

您可以看到，上述记录都是不同的。这让我们看到了文档数据库的最大优势。您不需要为记录设置固定的架构，并且每条记录都可以是任何有效的 JavaScript 表达式。

“动态”更改模式是使用 NoSQL 的最大优势。

现在，让我们尝试在数据库上执行上述插入查询。

      > db.students.insert(
...   [
...     {
...       "name": "Purushothaman",
...       "degree": "Management",
...       "email": "purush@example.com"
...     },
...     {
...       "name": "Meaow Meaow",
...       "degree": "Cat Study",
...       "email": "meaow@example.com",
...       "phone": ["9850420420"]
...     },
...   ]
... );
BulkWriteResult({
    "writeErrors" : [ ],
    "writeConcernErrors" : [ ],
    "nInserted" : 2,
    "nUpserted" : 0,
    "nMatched" : 0,
    "nModified" : 0,
    "nRemoved" : 0,
    "upserted" : [ ]
})
>
    

您将获得BulkWriteResult函数的输出，其中没有显示任何错误，并且插入的记录数为“2”。让我们使用find()方法快速检查表内容。

      > db.students.find();
{ "_id" : ObjectId("592ebe7e8e61243307417cc4"), "name" : "Praveen Kumar", "degree" : "Cloud Computing", "email" : "praveen@example.com", "subjects" : [ { "name" : "Internet Networks", "prof" : "Prof. Awesome Blossom" }, { "name" : "Cloud Computing", "prof" : "Prof. Tech Ninja" }, { "name" : "Web Development", "prof" : "Prof. Chunky Monkey" } ], "phone" : [ "9840035007", "9967728336", "7772844242" ] }
{ "_id" : ObjectId("592ed5818e61243307417cc5"), "name" : "Purushothaman", "degree" : "Management", "email" : "purush@example.com" }
{ "_id" : ObjectId("592ed5818e61243307417cc6"), "name" : "Meaow Meaow", "degree" : "Cat Study", "email" : "meaow@example.com", "phone" : [ "9850420420" ] }
>
    

我们得到了三条记录，每条记录都有不同的架构，这很棒！由于字段太多，让我们将其改为pretty()：

      > db.students.find().pretty();
{
    "_id" : ObjectId("592ebe7e8e61243307417cc4"),
    "name" : "Praveen Kumar",
    "degree" : "Cloud Computing",
    "email" : "praveen@example.com",
    "subjects" : [
        {
            "name" : "Internet Networks",
            "prof" : "Prof. Awesome Blossom"
        },
        {
            "name" : "Cloud Computing",
            "prof" : "Prof. Tech Ninja"
        },
        {
            "name" : "Web Development",
            "prof" : "Prof. Chunky Monkey"
        }
    ],
    "phone" : [
        "9840035007",
        "9967728336",
        "7772844242"
    ]
}
{
    "_id" : ObjectId("592ed5818e61243307417cc5"),
    "name" : "Purushothaman",
    "degree" : "Management",
    "email" : "purush@example.com"
}
{
    "_id" : ObjectId("592ed5818e61243307417cc6"),
    "name" : "Meaow Meaow",
    "degree" : "Cat Study",
    "email" : "meaow@example.com",
    "phone" : [
        "9850420420"
    ]
}
>
    

啊！就这样！

查询记录

为了查询或过滤字段，我们需要将它们作为参数对象传递给 find ()函数。举个例子，让我们看看我是否能用Meaow Meaow获取记录：

      > db.students.find({"name" : "Meaow Meaow"});
{ "_id" : ObjectId("592ed5818e61243307417cc6"), "name" : "Meaow Meaow", "degree" : "Cat Study", "email" : "meaow@example.com", "phone" : [ "9850420420" ] }
>
    

和往常一样，我们的pretty()会返回：

      > db.students.find({"name" : "Meaow Meaow"}).pretty();
{
    "_id" : ObjectId("592ed5818e61243307417cc6"),
    "name" : "Meaow Meaow",
    "degree" : "Cat Study",
    "email" : "meaow@example.com",
    "phone" : [
        "9850420420"
    ]
}
>
    

这也适用于数组中的项。find()方法在此处对值进行精确匹配。以下是另一个在数组中匹配数字的示例：

      > db.students.find({"phone": "9840035007"}).pretty();
{
    "_id" : ObjectId("592ebe7e8e61243307417cc4"),
    "name" : "Praveen Kumar",
    "degree" : "Cloud Computing",
    "email" : "praveen@example.com",
    "subjects" : [
        {
            "name" : "Internet Networks",
            "prof" : "Prof. Awesome Blossom"
        },
        {
            "name" : "Cloud Computing",
            "prof" : "Prof. Tech Ninja"
        },
        {
            "name" : "Web Development",
            "prof" : "Prof. Chunky Monkey"
        }
    ],
    "phone" : [
        "9840035007",
        "9967728336",
        "7772844242"
    ]
}
>
    

尽管9840035007只是现有的三个数字之一，上述命令仍能正确识别我的记录并显示它。

更新记录

这里我们使用的方法是db.collection.update()。它接受两个参数，第一个参数是记录中存在的匹配项的键值对对象。下一个参数是第一个参数应该替换的内容。

因此让我们尝试这样的事情：

      db.students.update(
  { name: "Praveen Kumar" },
  {
    name: "Praveen Kumar",
    degree: "Cloud Computing MSc",
    email: "praveen@example.net",
    subjects: [
      {
        name: "Internet Networks",
        prof: "Prof. Awesome Blossom"
      },
      {
        name: "Cloud Computing",
        prof: "Prof. Tech Ninja"
      },
      {
        name: "Web Development",
        prof: "Prof. Chunky Monkey"
      }
    ],
    phone: ["9840035007", "9967728336", "7772844242"]
  }
);
    

注意 1：如果使用更新函数，则需要提供完整对象，因为它会用第二个参数替换整个记录。如果我们没有设置其他值，它将只有一条记录，其中只有两个项目：电子邮件和学位。

注意 2：尽可能不要像我刚才那样按名称查找。可能有许多记录与同一参数匹配，因此请使用诸如_id之类的唯一名称。

尝试上述方法，我们得到：

      > db.students.update({"name": "Praveen Kumar"}, {
...   "name": "Praveen Kumar",
...   "degree": "Cloud Computing MSc",
...   "email": "praveen@example.net",
...   "subjects": [
...     {
...       "name": "Internet Networks",
...       "prof": "Prof. Awesome Blossom"
...     },
...     {
...       "name": "Cloud Computing",
...       "prof": "Prof. Tech Ninja"
...     },
...     {
...       "name": "Web Development",
...       "prof": "Prof. Chunky Monkey"
...     }
...   ],
...   "phone": ["9840035007", "9967728336", "7772844242"]
... });
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
>
    

瞧！让我们看看结果：

      {
  "nMatched": 1,
  "nUpserted": 0,
  "nModified": 1
}
    

它匹配了一条记录并对其进行了修改。没有更新记录（我们稍后会介绍）。这意味着它有可能匹配，但不会更新。让我们再次运行相同的命令，看看会发生什么。

哦天哪！输出结果是一样的。也许我太热情了。

要查看发生了什么变化，我们可以尝试运行find()函数以及 pretty ()函数。

      > db.students.find({"phone": "9840035007"}).pretty();
{
    "_id" : ObjectId("592ebe7e8e61243307417cc4"),
    "name" : "Praveen Kumar",
    "degree" : "Cloud Computing MSc",
    "email" : "praveen@example.net",
    "subjects" : [
        {
            "name" : "Internet Networks",
            "prof" : "Prof. Awesome Blossom"
        },
        {
            "name" : "Cloud Computing",
            "prof" : "Prof. Tech Ninja"
        },
        {
            "name" : "Web Development",
            "prof" : "Prof. Chunky Monkey"
        }
    ],
    "phone" : [
        "9840035007",
        "9967728336",
        "7772844242"
    ]
}
>
    

使用 $set

为了更改一个值而重新添加整个记录是一件很麻烦的事情。好消息是，有一种方法可以解决这个问题：使用$set运算符。假设我们需要将我的电子邮件地址更改为<font style="vertical-align: inherit;

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MongoDB 简介 - 记录和值

杭州电子商务研究院

5年前 · 面向社会、服务行业、政产学研结合、整合资源、和谐发展

db.students.insert([ { name: "Purushothaman", degree: "Management", email: "purush@example.com" }, { name: "Meaow Meaow", degree: "Cat Study", email: "meaow@example.com", phone: ["9850420420"] } ]);

> db.students.insert( ... [ ... { ... "name": "Purushothaman", ... "degree": "Management", ... "email": "purush@example.com" ... }, ... { ... "name": "Meaow Meaow", ... "degree": "Cat Study", ... "email": "meaow@example.com", ... "phone": ["9850420420"] ... }, ... ] ... ); BulkWriteResult({ "writeErrors" : [ ], "writeConcernErrors" : [ ], "nInserted" : 2, "nUpserted" : 0, "nMatched" : 0, "nModified" : 0, "nRemoved" : 0, "upserted" : [ ] }) >

> db.students.find(); { "_id" : ObjectId("592ebe7e8e61243307417cc4"), "name" : "Praveen Kumar", "degree" : "Cloud Computing", "email" : "praveen@example.com", "subjects" : [ { "name" : "Internet Networks", "prof" : "Prof. Awesome Blossom" }, { "name" : "Cloud Computing", "prof" : "Prof. Tech Ninja" }, { "name" : "Web Development", "prof" : "Prof. Chunky Monkey" } ], "phone" : [ "9840035007", "9967728336", "7772844242" ] } { "_id" : ObjectId("592ed5818e61243307417cc5"), "name" : "Purushothaman", "degree" : "Management", "email" : "purush@example.com" } { "_id" : ObjectId("592ed5818e61243307417cc6"), "name" : "Meaow Meaow", "degree" : "Cat Study", "email" : "meaow@example.com", "phone" : [ "9850420420" ] } >

> db.students.find().pretty(); { "_id" : ObjectId("592ebe7e8e61243307417cc4"), "name" : "Praveen Kumar", "degree" : "Cloud Computing", "email" : "praveen@example.com", "subjects" : [ { "name" : "Internet Networks", "prof" : "Prof. Awesome Blossom" }, { "name" : "Cloud Computing", "prof" : "Prof. Tech Ninja" }, { "name" : "Web Development", "prof" : "Prof. Chunky Monkey" } ], "phone" : [ "9840035007", "9967728336", "7772844242" ] } { "_id" : ObjectId("592ed5818e61243307417cc5"), "name" : "Purushothaman", "degree" : "Management", "email" : "purush@example.com" } { "_id" : ObjectId("592ed5818e61243307417cc6"), "name" : "Meaow Meaow", "degree" : "Cat Study", "email" : "meaow@example.com", "phone" : [ "9850420420" ] } >

> db.students.find({"name" : "Meaow Meaow"}); { "_id" : ObjectId("592ed5818e61243307417cc6"), "name" : "Meaow Meaow", "degree" : "Cat Study", "email" : "meaow@example.com", "phone" : [ "9850420420" ] } >

> db.students.find({"name" : "Meaow Meaow"}).pretty(); { "_id" : ObjectId("592ed5818e61243307417cc6"), "name" : "Meaow Meaow", "degree" : "Cat Study", "email" : "meaow@example.com", "phone" : [ "9850420420" ] } >

> db.students.find({"phone": "9840035007"}).pretty(); { "_id" : ObjectId("592ebe7e8e61243307417cc4"), "name" : "Praveen Kumar", "degree" : "Cloud Computing", "email" : "praveen@example.com", "subjects" : [ { "name" : "Internet Networks", "prof" : "Prof. Awesome Blossom" }, { "name" : "Cloud Computing", "prof" : "Prof. Tech Ninja" }, { "name" : "Web Development", "prof" : "Prof. Chunky Monkey" } ], "phone" : [ "9840035007", "9967728336", "7772844242" ] } >

db.students.update( { name: "Praveen Kumar" }, { name: "Praveen Kumar", degree: "Cloud Computing MSc", email: "praveen@example.net", subjects: [ { name: "Internet Networks", prof: "Prof. Awesome Blossom" }, { name: "Cloud Computing", prof: "Prof. Tech Ninja" }, { name: "Web Development", prof: "Prof. Chunky Monkey" } ], phone: ["9840035007", "9967728336", "7772844242"] } );

> db.students.update({"name": "Praveen Kumar"}, { ... "name": "Praveen Kumar", ... "degree": "Cloud Computing MSc", ... "email": "praveen@example.net", ... "subjects": [ ... { ... "name": "Internet Networks", ... "prof": "Prof. Awesome Blossom" ... }, ... { ... "name": "Cloud Computing", ... "prof": "Prof. Tech Ninja" ... }, ... { ... "name": "Web Development", ... "prof": "Prof. Chunky Monkey" ... } ... ], ... "phone": ["9840035007", "9967728336", "7772844242"] ... }); WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 }) >

> db.students.find({"phone": "9840035007"}).pretty(); { "_id" : ObjectId("592ebe7e8e61243307417cc4"), "name" : "Praveen Kumar", "degree" : "Cloud Computing MSc", "email" : "praveen@example.net", "subjects" : [ { "name" : "Internet Networks", "prof" : "Prof. Awesome Blossom" }, { "name" : "Cloud Computing", "prof" : "Prof. Tech Ninja" }, { "name" : "Web Development", "prof" : "Prof. Chunky Monkey" } ], "phone" : [ "9840035007", "9967728336", "7772844242" ] } >