how to query mongodb in java

",...," Coln ":" column value n "}) 2. find 2.1 All queries Syntax: db. Set. find () 2.2 conditional Query Syntax: db. Set. find ({"Col1": "column value 1", "Col2": "column value 2 ",...," Coln ":" column value n "}) Operation example: Add + search Note: The "_ id" field is the GUID that the database uses by default to ensure data uniqueness. 3. Modify 3.1 modify update all Syntax: db. Set. update ({"Col": "column value" },{ "Col2": "column value 2 "

getCollection method of the db object. In this way, a DBCollection is obtained, which is equivalent to the "table" of our database ". Query all data Complete source code 2. To complete the CRUD operation, first create MongoDB4CRUDTest. java. The basic test code is as follows: 3. Add operation Before adding an operation, we need to write a query method to

Tags: UI directory lin rdl hat enqueued Tor it comes withThere is a need: tracking MongoDB SQL statements and slow query collection Step one: Use the MongoDB self-function to see how many DML statements have been run over a period of time. Run under the bin directory./mongostat-port Port number you can see the following data Its output has the following columns:

, just use one point. More detailed can see this link: dot notationAs an example:> Db.blog.save ({title: "My first Post", Author: {Name: "Jane", Id:1}})If we want to query authors name is Jane, we can do this:> Db.blog.findOne ({"Author.name": "Jane"})If not, then you need to use the following sentence to match:Db.blog.findOne ({"Author": {"name": "Jane", "id": 1}})The following sentence:Db.blog.findOne ({"Author": {"name": "Jane"}})is not matched, be

equality of NULL as an element in the array, even if there is only one element in the array. Then there is the $exists determination of whether the specified key exists.> db.test.find({"x": {"$in": [null], "$exists":true}}){ "_id" : ObjectId("4fd59d30b9ac507e96276f1b"), "x" : null } Regular queries The regular syntax for Perl rules is used in MongoDB. Such as:> db.test.find(){ "_id" : ObjectId("4fd59ed7b9ac507e96276f1d"), "name" : "step

Tags: MongoDB queryStatement: The article is mainly from the "MongoDB actual Combat" a book, the main want to learn MongoDB knowledge through the book, deepen understanding, so write in their own blog, as a record, in the final chapter, there will be a collection of MongoDB database application

Test the effect of the key location on the query in MongoDB: 50 MongoDB development skills: the article "accelerated scanning by establishing hierarchical documents" explains that proper Chromatography can reduce MongoDB's access to fields and increase the speed. I have never thought of such a situation before, but I have never heard of it in relational databases

The previous article introduced how to conduct distributed storage of Relational Data Based on Mongodb. With storage, queries will be involved. Although it can be queried in a common way, we will introduce how to use the MapReduce function provided in MONGODB for query today.I have written an article about MongoDb MapR

1. Basic query: Constructs query data. Copy Code code as follows: > Db.test.findOne () { "_id": ObjectId ("4fd58ecbb9ac507e96276f1a"), "Name": "Stephen", "Age": 35, "Genda": "Male", "Email": "stephen@hotmail.com" } --Multi-condition query. The following example is equivalent to the WHERE name = "Stephen" and age = 35 of the SQL statement >

There are a lot of blog posts about how to take a single record out of a MongoDB library, including the following three ways:1. Skip a random number of records.dbcursor cursor = coll.find (query), int rint = Random.nextint (Cursor.count ()), Cursor.skip (rint);D bobject word = null;if ( Cursor.hasnext ()) {word = Cursor.next (); Cursor.close ();}Many people say that this is not recommended, if the amount of

[Switch] The internal implementation of IMongoQuery in MongoDB C #/. NET Driver, MongoDB is a product between relational databases and non-relational databases. It has the most abundant functions and features like relational databases. The supported data structure is very loose and is similar to the json bjson format. Therefore, it can store complicated data types. The biggest feature of Mongo is that it su

The official MongoDB documentation shows that the overwrite query is the following query: All query fields are part of the index All the query return fields are in the same index Because all fields that appear in the qu