在 MongoDB 中获取不同的记录值?
mongodbdatabasebig data analytics更新于 2026/1/19 6:37:17
您可以使用 MongoDB 中的 distinct() 方法获取不同的记录值。语法如下:−
db.yourCollectionName.distinct(“yourFieldName”);
为了理解上述语法，让我们创建一个包含 document 的集合。创建包含 document 的集合的查询如下 −
> db.distinctRecordDemo.insertOne({"StudentId":1,"StudentName":"John","StudentAge":21});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c77a78299b97a65744c1b50")
}
> db.distinctRecordDemo.insertOne({"StudentId":2,"StudentName":"John","StudentAge":22});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c77a78b99b97a65744c1b51")
}
> db.distinctRecordDemo.insertOne({"StudentId":3,"StudentName":"Carol","StudentAge":21});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c77a79a99b97a65744c1b52")
}
> db.distinctRecordDemo.insertOne({"StudentId":4,"StudentName":"Carol","StudentAge":26});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c77a7a499b97a65744c1b53")
}
> db.distinctRecordDemo.insertOne({"StudentId":5,"StudentName":"Sam","StudentAge":24});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c77a7b499b97a65744c1b54")
}
> db.distinctRecordDemo.insertOne({"StudentId":6,"StudentName":"Mike","StudentAge":27});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c77a7c799b97a65744c1b55")
}
> db.distinctRecordDemo.insertOne({"StudentId":7,"StudentName":"Sam","StudentAge":28});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c77a7d399b97a65744c1b56")
}
使用 find() 方法显示集合中的所有文档。查询如下 −
> db.distinctRecordDemo.find().pretty();
输出结果如下:
{
"_id" : ObjectId("5c77a78299b97a65744c1b50"),
"StudentId" : 1,
"StudentName" : "John",
"StudentAge" : 21
}
{
"_id" : ObjectId("5c77a78b99b97a65744c1b51"),
"StudentId" : 2,
"StudentName" : "John",
"StudentAge" : 22
}
{
"_id" : ObjectId("5c77a79a99b97a65744c1b52"),
"StudentId" : 3,
"StudentName" : "Carol",
"StudentAge" : 21
}
{
"_id" : ObjectId("5c77a7a499b97a65744c1b53"),
"StudentId" : 4,
"StudentName" : "Carol",
"StudentAge" : 26
}
{
"_id" : ObjectId("5c77a7b499b97a65744c1b54"),
"StudentId" : 5,
"StudentName" : "Sam",
"StudentAge" : 24
}
{
"_id" : ObjectId("5c77a7c799b97a65744c1b55"),
"StudentId" : 6,
"StudentName" : "Mike",
"StudentAge" : 27
}
{
"_id" : ObjectId("5c77a7d399b97a65744c1b56"),
"StudentId" : 7,
"StudentName" : "Sam",
"StudentAge" : 28
}
以下是在 MongoDB 中获取不同记录值的查询。
案例 1 − 这里的字段是 “StudentName”。
查询如下 −
> db.distinctRecordDemo.distinct("StudentName");
以下是显示 StudentName 的不同记录的输出 −
[ "John", "Carol", "Sam", "Mike" ]
案例 2 −此处字段为"StudentAge"。
查询如下 −
> db.distinctRecordDemo.distinct("StudentAge");
以下输出显示 StudentAge 的不同记录−
[ 21, 22, 26, 24, 27, 28 ]
