Let us first create a collection with documents -> db.removingAnArrayElementDemo.insertOne({"UserMessage":["Hi", "Hello", "Bye"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cef97bdef71edecf6a1f6a4") }Display all documents from a collection with the help of find() method -> db.removingAnArrayElementDemo.find().pretty();Output{    "_id" : ObjectId("5cef97bdef71edecf6a1f6a4"),    "UserMessage" : [       "Hi",       "Hello",       "Bye"    ] }Following is the query to remove an array element from MongoDB -> db.removingAnArrayElementDemo.update(    {_id:ObjectId("5cef97bdef71edecf6a1f6a4")},    { "$pull": { "UserMessage": "Hello" } } ); WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })Let us check the document once again:> db.removingAnArrayElementDemo.find().pretty();Output{   ... Read More

Let us first create a collection with documents -> db.operatorDemo.insertOne({"StudentSubject":["MongoDB", "MySQL", "Java"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cef94eaef71edecf6a1f6a2") } > db.operatorDemo.insertOne({"StudentSubject":["Java", "C", "C++"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5cef94faef71edecf6a1f6a3") }Display all documents from a collection with the help of find() method -> db.operatorDemo.find().pretty();Output{    "_id" : ObjectId("5cef94eaef71edecf6a1f6a2"),    "StudentSubject" : [       "MongoDB",       "MySQL",       "Java"    ] } {    "_id" : ObjectId("5cef94faef71edecf6a1f6a3"),    "StudentSubject" : [       "Java",       "C",       "C++"    ] }Following is the query for ... Read More

Let us first create a table −mysql> create table DemoTable1    (    value int    ); Query OK, 0 rows affected (0.59 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1 values(10); Query OK, 1 row affected (0.17 sec)Display all records from the table using select statement −mysql> select *from DemoTable1;Output+-------+ | value | +-------+ | 10 | +-------+ 1 row in set (0.00 sec)Following is the query to create second table −mysql> create table DemoTable2    (    value1 int    ); Query OK, 0 rows affected (0.62 sec)Insert some records in the table ... Read More

To set all the values in a field to 0, use the update command −update yourTableName set yourColumnName=0;Let us first create a table −mysql> create table DemoTable    (    Number int    ); Query OK, 0 rows affected (0.64 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(10); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values(4757); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values(48474); Query OK, 1 row affected (0.26 sec) mysql> insert into DemoTable values(35465); Query OK, 1 row affected (0.16 sec)Display all records from ... Read More

Let us first create a table −mysql> create table DemoTable    (    Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    StudentName varchar(20)    ); Query OK, 0 rows affected (1.23 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(StudentName) values('John'); Query OK, 1 row affected (0.08 sec) mysql> insert into DemoTable(StudentName) values('Carol'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable(StudentName) values('David'); Query OK, 1 row affected (0.07 sec) mysql> insert into DemoTable(StudentName) values('Bob'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable(StudentName) values('Chris'); Query OK, 1 row affected (0.12 sec) ... Read More

To get the last days of all the months, use the LAST_DAY() function from MySQL −SELECT LAST_DAY(yourColumnName) from yourTableName;Let us first create a table −mysql> create table DemoTable    (    ShippingDate date    ); Query OK, 0 rows affected (0.69 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('2019-01-12'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable values('2019-02-01'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values('2019-03-04'); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable values('2019-04-21'); Query OK, 1 row affected (0.14 sec)Display all records ... Read More

Use the concept of DATE_SUB(). Let us first create a table −mysql> create table DemoTable    (    Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    ArrivalDate datetime    ); Query OK, 0 rows affected (1.02 sec)Note: Let’s say the current date is 2019-06-08Insert some records in the table using insert command −mysql> insert into DemoTable(ArrivalDate) values('2019-05-15'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable(ArrivalDate) values('2019-06-08'); Query OK, 1 row affected (0.24 sec) mysql> insert into DemoTable(ArrivalDate) values('2019-05-20'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable(ArrivalDate) values('2019-05-12'); Query OK, 1 row affected (0.12 sec)Display ... Read More

To delete all rows except a single specific row, try the below syntax −delete from yourTableName where yourColumnName!=yourValue;Let us first create a table −mysql> create table DemoTable    (    Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    Subject varchar(100)    ); Query OK, 0 rows affected (0.65 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(Subject) values('MySQL'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable(Subject) values('MongoDB'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable(Subject) values('Java'); Query OK, 1 row affected (0.12 sec)Display all records from the table using select ... Read More

You can use CONCAT() for this. The syntax is as follows −insert into DemoTable values(concat(curdate(), ' yourSpecificTime’));Let us first create a table −mysql> create table DemoTable    (    ArrivalDate datetime    ); Query OK, 0 rows affected (1.06 sec)Insert some records in the table using insert command. We are adding the current date and time −mysql> insert into DemoTable values(concat(curdate(), ' 10:20:05')); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values(concat(curdate(), ' 12:05:00')); Query OK, 1 row affected (0.17 sec)Display all records from the table using select statement −mysql> select *from DemoTable;Output+---------------------+ | ArrivalDate ... Read More

You can use delete command −delete from yourTableName where yourColumnName='\\';Let us first create a table −mysql> create table DemoTable    (    FolderName varchar(100)    ); Query OK, 0 rows affected (0.67 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values("????"); Query OK, 1 row affected (0.44 sec) mysql> insert into DemoTable values("\\"); Query OK, 1 row affected (0.13 sec)Display all records from the table using select statement −mysql> select *from DemoTable;Output+------------+ | FolderName | +------------+ | ???? | | \ ... Read More