The strol() function is used to convert the string to long integers. It sets the pointer to point to the first character after the last one. The syntax is like below. This function is present into the cstdlib library.long int strtol(const char* str, char ** end, int base)This function takes ... Read More

Use unique and set it to TRUE. Let us implement the same by creating index and setting two columns to unique −>db.keepTwoColumnsUniqueDemo.createIndex({"StudentFirstName":1, "StudentLastName":1}, {unique:true}); {    "createdCollectionAutomatically" : true,    "numIndexesBefore" : 1,    "numIndexesAfter" : 2,    "ok" : 1 }Now you can insert documents in the above collection ... Read More

You can use $where operator for this. Let us first create a collection with documents −>db.veryStrictDocumentDemo.insertOne({"StudentFirstName":"John", "StudentLastName":"Doe", "StudentAge":23}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cda4bcdb50a6c6dd317adb8") } > db.veryStrictDocumentDemo.insertOne({"StudentFirstName":"Larry"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cda4bdbb50a6c6dd317adb9") } >db.veryStrictDocumentDemo.insertOne({"StudentFirstName":"David", "StudentLastName":"Miller"}); {    "acknowledged" : true,    "insertedId" : ... Read More

Here we will see one interesting problem. In this problem, we will see how to print Christmas tree randomly. So the tree will be flickering like Christmas tree lights.To print a Christmas tree, we will print pyramids of various sizes just one beneath another. For the decorative leaves a random ... Read More

Let us first create a collection with documents −> db.projectionAnElementDemo.insertOne( ...    { ...       "CustomerId":100, ...       "CustomerDetails": [ ...          { ...             "CustomerName": "Chris", ...             "CustomerCountryName": "US" ...   ... Read More

You need to use multi:true to update multiple documents. Let us first create a collection with documents −> db.multiUpdateDemo.insertOne({"ClientName":"John", "ClientAge":29}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cda5bc0b50a6c6dd317adc8") } > db.multiUpdateDemo.insertOne({"ClientName":"Carol", "ClientAge":31}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cda5bc1b50a6c6dd317adc9") } > db.multiUpdateDemo.insertOne({"ClientName":"John", "ClientAge":39}); {    "acknowledged" : ... Read More

In the cstdlib library of C++, there are different functions for getting the absolute value except from abs. The abs are used basically for int type input in C, and int, long, long long in C++. The others are used for long, and long long type data etc. Let us ... Read More

To highlight a row in a table, you can use the addRowSelectionInterval() method. At first create a table −DefaultTableModel tableModel = new DefaultTableModel(); JTable table = new JTable(tableModel);Add some columns −tableModel.addColumn("Language/ Technology"); tableModel.addColumn("Text Tutorial"); tableModel.addColumn("Video Tutorial"); tableModel.addColumn("Views");Now, add rows to the table −tableModel.addRow(new Object[] { "NodeJS", "No", "Yes", "2350"}); tableModel.addRow(new ... Read More

If you will try to use the method drop(), then it will delete all information about the collection. Indexing is fast. However, if you will use the method remove(), then it removes all records but keeps the collection and indexes.Let us check with the help of example.Using drop()Let us first ... Read More

We use gcc and g++ compilers in different times. Here we will see what are the differences between gcc and g++.The gcc is GNU C compiler, and g++ is GNU C++ compiler. The main differences are like below −gcc can compile *.c or *.cpp files as C and C++ respectivelyg++ ... Read More