How often you develop an application and you write same validation for every input fields. One such example is User registration, Login screen or Registration screen or any other screen. It becomes tedious to write same line of code for every input field moreover you may tend to mistake the ... Read More

You can use dot(.) notation for this. Let us first create a collection with documents −> db.createIndexOnNestedFieldDemo.insertOne(    {"UserDetails":{"UserPersonalDetails":{"UserFirstName":"John", "UserLastName":"Smith"}}});    {       "acknowledged" : true,       "insertedId" : ObjectId("5ce929c778f00858fb12e916")    } > > db.createIndexOnNestedFieldDemo.insertOne( {"UserDetails":{"UserPersonalDetails":{"UserFirstName":"Chris", "UserLastName":"Brown"}}}); {    "acknowledged" : true,    "insertedId" : ObjectId("5ce929d678f00858fb12e917") ... Read More

You need to use FIND_IN_SET() for this. Let us first create a table −mysql> create table DemoTable ( CustomerId int NOT NULL AUTO_INCREMENT PRIMARY KEY, CustomerName varchar(20), CustomerAllProductPrice text ); Query OK, 0 rows affected ... Read More

To update child objects, use $set operator. Let us first create a collection with document −>db.updateChildObjectsDemo.insertOne({"StudentName":"Chris", "StudentOtherDetails":{"StudentSubject":"MongoDB", "StudentCountryName":"AUS"}}); {    "acknowledged" : true,    "insertedId" : ObjectId("5ce964e078f00858fb12e91f") }Following is the query to display all documents from a collection with the help of find() method −> db.updateChildObjectsDemo.find().pretty();This will produce the following ... Read More

To insert when a record does not exist, set the column as UNIQUE INDEX. Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FirstName varchar(20) ); Query OK, 0 ... Read More

MongoDB supports the BSON format data, so there is no max length of field name. Let us first create a collection with documents −>db.maxLengthDemo.insertOne({"maxLengthhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh":"This is demo"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5ce97ac978f00858fb12e926") }Following is the query ... Read More

To fetch only N rows at a time, you can use LIMIT operator. Following is the syntax −select *from yourTableNameLIMIT 0, N;Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Name varchar(20) ... Read More

For this, use aggregate framework with the $elemMatch operator. Let us first create a collection with documents −> db.matchMultipleCriteriaDemo.insertOne({    "EmployeeDetails": [       {"EmployeeName": "Chris", "Salary": 45000, "Language":"Java"},       {"EmployeeName": "Robert", "Salary": 41000, "Language":"Python"}    ] }); {    "acknowledged" : true,    "insertedId" : ObjectId("5cea3bf0ef71edecf6a1f689") ... Read More

You can use elt() along with rand() for this. Let us select random number from a specific list.mysql> SELECT ELT(FLOOR(RAND() * 10) + 1,    100, 200, 300, 400, 500, 600, 700, 800, 900, 1000) AS random_value_from_listOfValues;This will produce the following output −+--------------------------------+ | random_value_from_listOfValues | +--------------------------------+ | 1000 ... Read More

To query array of nested string, you can use the dot(.) notation. Let us first create a collection with documents −> db.nestedStringDemo.insertOne(    {       "CustomerName": "John",       "CustomerOtherDetails": [ { "Age":29, "CountryName": "US" },       { "CompanyName": "Amazon",       "Salary": 150000, ... Read More