要在MongoDB中创建嵌套索引,可以使用createIndex()
或ensureIndex()
。语法如下-
db.yourCollectionName.createIndex({"yourOuterFieldName.yourInnerFieldName.yourSecondInnerFieldName": 1});
为了理解语法,让我们用文档创建一个集合。使用文档创建集合的查询如下-
> db.nestedIndexDemo.insertOne( ... { ... ... "CustomerId":101, ... "CustomerDetails": ... { ... "CustomerListDetails": ... { ... "CustomerName":"Larry", ... "CustomerProjectName": "Project-1", ... "CustomerCountryName":"US" ... } ... } ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5c8fc565d3c9d04998abf010") }
在find()
method的帮助下显示集合中的所有文档。查询如下-
> db.nestedIndexDemo.find().pretty();
以下是输出-
{ "_id" : ObjectId("5c8fc565d3c9d04998abf010"), "CustomerId" : 101, "CustomerDetails" : { "CustomerListDetails" : { "CustomerName" : "Larry", "CustomerProjectName" : "Project-1", "CustomerCountryName" : "US" } } }
这是在MongoDB中创建嵌套索引的查询:
> db.nestedIndexDemo.createIndex({"CustomerDetails.CustomerListDetails.CustomerCountryName": 1}); { "createdCollectionAutomatically" : false, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 }
这是显示索引的查询-
> db.nestedIndexDemo.getIndexes();
以下是输出-
[ { "v" : 2, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "test.nestedIndexDemo" }, { "v" : 2, "key" : { "CustomerDetails.CustomerListDetails.CustomerCountryName" : 1 }, "name" : "CustomerDetails.CustomerListDetails.CustomerCountryName_1", "ns" : "test.nestedIndexDemo" } ]