如何从MongoDB集合中删除重复项

2026-06-04 1 花语

为此，设置“unique：true”，即唯一约束，并避免插入重复项，如以下语法所示：db.yourCollectionName.ensureIndex({yourFieldName: 1}, {unique: true, dropDups: true})

为了理解上述语法，让我们创建一个包含文档的集合。在这里，不允许重复插入-

> db.demo604.ensureIndex({FirstName: 1}, {unique: true, dropDups: true});{ "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.demo604.insertOne({FirstName:"Chris"});{ "acknowledged" : true, "insertedId" : ObjectId("5e960887ed011c280a0905d8") } > db.demo604.insertOne({FirstName:"Bob"});{ "acknowledged" : true, "insertedId" : ObjectId("5e96088aed011c280a0905d9") } > db.demo604.insertOne({FirstName:"David"});{ "acknowledged" : true, "insertedId" : ObjectId("5e96088ded011c280a0905da") } > db.demo604.insertOne({FirstName:"Chris"}); 2020-04-15T00:31:35.978+0530 E QUERY [js] WriteError: E11000 duplicate key error collection: test.demo604 index: FirstName_1 dup key: { : "Chris" } : WriteError({ "index" : 0, "code" : 11000, "errmsg" : "E11000 duplicate key error collection: test.demo604 index: FirstName_1 dup key: { : \"Chris\" }", "op" : { "_id" : ObjectId("5e96088fed011c280a0905db"), "FirstName" : "Chris" } }) WriteError@src/mongo/shell/bulk_api.js:461:48 Bulk/mergeBatchResults@src/mongo/shell/bulk_api.js:841:49 Bulk/executeBatch@src/mongo/shell/bulk_api.js:906:13 Bulk/this.execute@src/mongo/shell/bulk_api.js:1150:21 DBCollection.prototype.insertOne@src/mongo/shell/crud_api.js:252:9 @(shell):1:1

在find()方法的帮助下显示集合中的所有文档-

> db.demo604.find();

这将产生以下输出-

{ "_id" : ObjectId("5e960887ed011c280a0905d8"), "FirstName" : "Chris" } { "_id" : ObjectId("5e96088aed011c280a0905d9"), "FirstName" : "Bob" } { "_id" : ObjectId("5e96088ded011c280a0905da"), "FirstName" : "David" }