MongoDB学习笔记-- 插入、查找

创建一个集合并向该集合中添加文档

当我们向某集合中插入文档时，如果该集合不存在，mongodb会自动创建该集合，不需手动创建集合，同时也不需要指定文档的结构。

创建并插入文档

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j = {name:"mongo"}
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k = {x:3}
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l <span></span>= {name:"wangwu"}
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db.testData.insert(j)
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db.testData.insert(k)
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db.testData.insert(l)

确认该集合是否存在

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show collections

查找

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db.testData.find()
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{ "_id" : ObjectId("4c2209f9f3924d31102bd84a"), "name" : "mongo" }
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{ "_id" : ObjectId("4c2209fef3924d31102bd84b"), "x" : 3 }

All MongoDB documents must have an _id field with a unique value. These operations do not explicitly specify a value for the _id field, so mongo creates a unique ObjectId value for the field before inserting it into the collection.

循环插入多个文档

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for (var i = 1; i <= 25; i++) db.testData.insert( { x : i } )

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{ "_id" : ObjectId("51a7dc7b2cacf40b79990be6"), "x" : 1 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990be7"), "x" : 2 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990be8"), "x" : 3 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990be9"), "x" : 4 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990bea"), "x" : 5 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990beb"), "x" : 6 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990bec"), "x" : 7 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990bed"), "x" : 8 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990bee"), "x" : 9 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990bef"), "x" : 10 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990bf0"), "x" : 11 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990bf1"), "x" : 12 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990bf2"), "x" : 13 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990bf3"), "x" : 14 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990bf4"), "x" : 15 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990bf5"), "x" : 16 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990bf6"), "x" : 17 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990bf7"), "x" : 18 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990bf8"), "x" : 19 }
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{ "_id" : ObjectId("51a7dc7b2cacf40b79990bf9"), "x" : 20 }

mongodb find() 默认只显示20条记录

find() 返回一个游标，迭代游标并返回更多的文档使用it操作在mongo shell。

通过Mongo Shell Function插入

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function insertData(dbName, colName, num) {
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  var col = db.getSiblingDB(dbName).getCollection(colName);
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  for (i = 0; i < num; i++) {
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    col.insert({x:i});
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  }
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  print(col.count());
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}
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insertData（"mydb", "testData", 200）
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db.testData.count()
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