You can use distinct keyword to select all values from a table only once if they are repeated.The syntax is as followsselect distinct yourColumnName from yourTableName;To understand the above syntax, let us create a table. The query to create a table is as follows.mysql> create table displayOnlyDistinctValue    -> (    -> UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY,    -> UserName varchar(100),    -> UserAge int    -> ); Query OK, 0 rows affected (0.47 sec)Insert some records in the table using insert command.The query is as follows.mysql> insert into displayOnlyDistinctValue(UserName, UserAge) values('Larry', 23); Query OK, 1 row affected ... Read More

To clear console in MongoDB, you can use any of the following two syntaxes.The first syntax is as follows, which is the usage of keyboard shortcut −Ctrl + LAfter pressing the above key, you can clear console in MongoDB.The second syntax is as follows −clsTo understand the above syntaxes, let us implement them one by one. Here is the snapshot of my console.The first query is as follows to clear console in MongoDB −Ctrl+L;The following is the output −Look at the above sample output, the console has been cleared. Let us check the console once again.The second query is as ... Read More

To select all entries from a particular month in MySQL, use the monthname() or month() function.The syntax is as follows.select *from yourTableName where monthname(yourColumnName)='yourMonthName';To understand the above syntax, let us create a table. The query to create a table is as followsmysql> create table selectAllEntriesDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> ShippingDate datetime -> ); Query OK, 0 rows affected (0.63 sec)Insert some records in the table using insert command.The query is as followsmysql> insert into selectAllEntriesDemo(ShippingDate) values('2019-01-21'); Query OK, 1 row affected ... Read More

You can use $pull operator to remove the object from an array in MongoDB. 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.removeObjectFromArrayDemo.insertOne( ... {    ...    ... "StudentName": "John",    ... "StudentAcademicProjectDetails":    ... [{          ... "StudentProjectId": 101,          ... "StudentProjectName": "Pig Dice Game"       ... },       ... {          ... "StudentProjectId": 110,          ... "StudentProjectName": "Library Management System"       ... ... Read More

MongoDB indexes every value of an array so that you can query for single elements.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.indexingForArrayElementDemo.insertOne({"StudentFavouriteSubject":["MongoDB", "MySQL"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c8acdca6cea1f28b7aa0816") }Display all documents from a collection with the help of find() method. The query is as follows −> db.indexingForArrayElementDemo.find().pretty();The following is the output −{    "_id" : ObjectId("5c8acdca6cea1f28b7aa0816"),    "StudentFavouriteSubject" : [       "MongoDB",       "MySQL"    ] }Here is the query by which MongoDB index ... Read More

You need to use ALTER TABLE command along with MODIFYThe syntax is as followsALTER TABLE yourTableName MODIFY COLUMN yourColumnName varchar(100) NOT NULL;To understand the above syntax, let us create a table. The query to create a table is as followsmysql> create table syntaxOfAlterCommandDemo    -> (    -> UserId int,    -> UserName varchar(30),    -> UserAge int,    -> UserCityName varchar(50)    -> ); Query OK, 0 rows affected (0.51 sec)Let us check the description of the table.The query is as followsmysql> desc syntaxOfAlterCommandDemo;The following is the output+--------------+-------------+------+-----+---------+-------+ | Field | Type ... Read More

To replace values in a table, use the CASE statement. To understand the concept, let us create a table. The query to create a table is as followsmysql> create table replaceValueDemo    -> (    -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    -> Name varchar(10),    -> isGreaterThan18 varchar(10)    -> ); Query OK, 0 rows affected (0.49 sec)Insert some records in the table using insert command.The query is as followsmysql> insert into replaceValueDemo(Name, isGreaterThan18) values('John', 'YES'); Query OK, 1 row affected (0.24 sec) mysql> insert into replaceValueDemo(Name, isGreaterThan18) values('Carol', 'NO'); Query OK, 1 row affected (0.16 sec) ... Read More

Let us first create a collection with the document. The query to create a collection with a document is as follows −> db.aggregationFrameworkWithOrMatchDemo.insertOne({"StudentFirstName":"John",    "StudentLastName":"Smith", "StudentAge":23}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c8ac3a96cea1f28b7aa080d") } > db.aggregationFrameworkWithOrMatchDemo.insertOne({"StudentFirstName":"Carol",    "StudentLastName":"Tayor", "StudentAge":24}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c8ac3bc6cea1f28b7aa080e") } > db.aggregationFrameworkWithOrMatchDemo.insertOne({"StudentFirstName":"David",    "StudentLastName":"Miller", "StudentAge":21}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c8ac3ce6cea1f28b7aa080f") } > db.aggregationFrameworkWithOrMatchDemo.insertOne({"StudentFirstName":"Bob",    "StudentLastName":"Taylor", "StudentAge":20}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c8ac3e16cea1f28b7aa0810") } > db.aggregationFrameworkWithOrMatchDemo.insertOne({"StudentFirstName":"Robert",    "StudentLastName":"Smith", "StudentAge":20}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c8ac3fb6cea1f28b7aa0811") } > db.aggregationFrameworkWithOrMatchDemo.insertOne({"StudentFirstName":"Mike",    "StudentLastName":"Miller", ... Read More

To retrieve time as HH:MM format, use the DATE_FORMAT() function. To understand the function and retrieve time, let us create a table.The query to create a table is as followsmysql> create table retrieveTimeDemo    -> (    -> UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY,    -> UserArrivalTime datetime    -> ); Query OK, 0 rows affected (0.57 sec)Insert some records in the table using insert command.The query is as followsmysql> insert into retrieveTimeDemo(UserArrivalTime) values('2013-01-21 13:45:34'); Query OK, 1 row affected (0.16 sec) mysql> insert into retrieveTimeDemo(UserArrivalTime) values('2014-11-25 11:40:56'); Query OK, 1 row affected (0.11 sec) mysql> insert into retrieveTimeDemo(UserArrivalTime) ... Read More

To query condition on comparing 2 fields, use the following syntax −db.yourCollectionName.find( { $where: function() { return this.yourFirstFieldName < this.yourSecondFieldName } } ).pretty();To understand the syntax, let us create a collection with the document. The query to create a collection with a document is as follows −> db.comparingTwoFieldsDemo.insertOne({"StudentName":"John", "StudentAge":21, "StudentMathMarks":99, "StudentPhysicsMarks":98}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c8ac09e6cea1f28b7aa0807") } > db.comparingTwoFieldsDemo.insertOne({"StudentName":"Carol", "StudentAge":22, "StudentMathMarks":79, "StudentPhysicsMarks":89}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c8ac0b46cea1f28b7aa0808") } > db.comparingTwoFieldsDemo.insertOne({"StudentName":"David", "StudentAge":24, "StudentMathMarks":39, "StudentPhysicsMarks":45}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c8ac0c96cea1f28b7aa0809") } > db.comparingTwoFieldsDemo.insertOne({"StudentName":"Bob", "StudentAge":23, "StudentMathMarks":87, "StudentPhysicsMarks":78}); {    "acknowledged" : ... Read More