The syntax is as follows for the $or query in MongoDB −db.yourCollectionName.find({ $or : [ { "yourFieldName" : "yourValue1" }, {"yourFieldName":"yourValue2"}, ...........N ] } ).pretty();To understand the concept, let us create a collection with the document. The query to create a collection with a document is as follows −> db.orDemo.insertOne({"UserName":"Larry", ... Read More

unordered_multimap size() function in C++ STL returns the number of elements in the unordered map.AlgorithmBegin    Declare an empty map container m.    Performing reserve function to restrict the most appropriate    bucket_count of the map container.    Insert values in the map container.    Print the size of the ... Read More

Before getting into example, we should know what sqlite data base in android is. SQLite is an open source SQL database that stores data to a text file on a device. Android comes in with built in SQLite database implementation. SQLite supports all the relational database features. In order to ... Read More

vector insert() function in C++ STL helps to increase the size of a container by inserting the new elements before the elements at the specified position.It is a predefined function in C++ STL.We can insert values with three types of syntaxes1. Insert values by mentioning only the position and value:vector_name.insert(pos, ... Read More

In order to return static strings in MySQL, you can use UNION. Following is the syntax −select 'yourStringValue1' as yourAliasName UNION select 'yourStringValue2' as yourAliasName;Let us implement the above syntax to return static strings in MySQL. Following is the query −mysql> select 'HELLO' as staticStringsResult    -> UNION    -> ... Read More

Before getting into example, we should know what sqlite data base in android is. SQLite is an open source SQL database that stores data to a text file on a device. Android comes in with built in SQLite database implementation. SQLite supports all the relational database features. In order to ... Read More

In order to stop MongoDB in a single command, use the following syntax −mongo --eval "db.getSiblingDB('admin').shutdownServer()"Let us implement the above syntax in order to stop MongoDB in one command.First, use the shortcut key −Ctrl + C;The query is as follows −C:\Program Files\MongoDB\Server\4.0\bin>mongo --eval "db.getSiblingDB('admin').shutdownServer()"The following is the output − displaying ... Read More

Yes, you can set Auto Increment later with ALTER table. Let us first create a table. Here, as you can see, we haven’t set Auto Increment −mysql> create table forgetToSetAutoIncrementDemo    -> (    -> StudentId int,    -> StudentName varchar(30)    -> ); Query OK, 0 rows affected (1.17 ... Read More

To form a composite key to be unique, you need to use ADD UNIQUE command. Following is the syntax −alter table yourTableName add unique yourUniqueName( yourColumnName1, yourColumnName2, .......N);Let us first create a table. Following is the query −mysql> create table makeCompositeKeyDemo    -> (    -> Id int NOT NULL ... Read More

To identify the last document from MongoDB find() result set, you can use sort() in descending order. The syntax is as follows −db.yourCollectionName.find().sort( { _id : -1 } ).limit(1).pretty();To understand the above syntax, let us create a collection with the document. The query to create a collection with a document ... Read More