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Articles by Nishtha Thakur
Page 26 of 40
MongoDB query to remove empty objects in an object-array?
You can use $pull operator for this. Let us first create a collection with documents. Here, we have also added an empty object −> db.removeEmptyObjectsDemo.insertOne( { "_id" :101, "LoginDate" :new ISODate(), "UserDetails" : [ { "UserName" : "John" }, { }, { "UserName" : "Sam" } ] } ); { ...
Read MoreMongoDB query to update an array element matching a condition using $push?
Let us first create a collection with documents −> db.updateArrayElementDemo.insertOne( { "UserDetails": [ { "UserName":"Chris", "UserAge":23 } ] } ); { "acknowledged" : true, "insertedId" : ObjectId("5ce9029378f00858fb12e90d") }Following is the query to display all documents from a collection with the help of find() method −> db.updateArrayElementDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5ce9029378f00858fb12e90d"), "UserDetails" : [ { ...
Read MoreUpdating boolean value in MySQL?
To update boolean value, you can use SET. Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, isMarried boolean ); Query OK, 0 rows affected (0.58 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(isMarried) values(false); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable(isMarried) values(true); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable(isMarried) values(true); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable(isMarried) values(false); Query OK, 1 row affected (0.13 sec)Display all records ...
Read MoreFind documents where all elements of an array have a specific value in MongoDB?\\n
You can use find() for this. Let us first create a collection with documents −> db.findDocumentsDemo.insertOne( { _id: 101, "ProductDetails": [ { "ProductValue":100 }, { "ProductValue":120 } ] } ); { "acknowledged" : true, "insertedId" : 101 } > db.findDocumentsDemo.insertOne( { _id: 102, "ProductDetails": [ { "ProductValue":120}, { "ProductValue":120 }, { "ProductValue":120 } ] } ); { "acknowledged" ...
Read MorePerforming mathematical operations in MySQL IF then ELSE is possible?
For performing mathematical operations and working with conditions, you can consider CASE statement. Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FruitName varchar(100), FruitPrice int ); Query OK, 0 rows affected (0.26 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(FruitName, FruitPrice) values('Orange', 250); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable(FruitName, FruitPrice) values('Banana', 100); Query OK, 1 row affected (0.05 sec) mysql> insert into DemoTable(FruitName, FruitPrice) values('Apple', 150); Query OK, 1 row affected (0.05 sec) ...
Read MoreConvert a field to an array using MongoDB update operation?
To convert a field to an array, use $set operator. Let us first create a collection with documents −> db.convertAFieldToAnArrayDemo.insertOne({"StudentSubject":"MongoDB"}); { "acknowledged" : true, "insertedId" : ObjectId("5ce92d7778f00858fb12e91d") }Following is the query to display all documents from a collection with the help of find() method −> db.convertAFieldToAnArrayDemo.find();This will produce the following output −{ "_id" : ObjectId("5ce92d7778f00858fb12e91d"), "StudentSubject" : "MongoDB" }Following is the query to convert a field to an array using update operation with $set:−> db.convertAFieldToAnArrayDemo.find().forEach(function(myDocument) { db.convertAFieldToAnArrayDemo.update( { _id: myDocument._id }, { "$set": { "StudentSubject": [myDocument.StudentSubject] } } ); })Let ...
Read MoreAdding new column after a specific column and defining a default in MySQL?
You need to follow some steps to add a new column after a specific column and defining default value. In order to achieve this, you need to use ALTER command. Let us first create a table −mysql> create table DemoTable ( StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, StudentFirstName varchar(20), StudentAge int, StudentCountryName varchar(100) ); Query OK, 0 rows affected (0.21 sec)Let us check the description of table −mysql> desc DemoTable;This will produce the following output −+--------------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | ...
Read MoreUpdate a single list item of a MongoDB document?
To update a single list item, use positional operator($). Let us first create a collection with documents −> db.updateASingleListDemo.insertOne({ _id:1, "EmployeeName":"Chris", "EmployeeDetails": [ {"EmployeeId":"EMP-101", "EmployeeSalary": 18999 }] }); { "acknowledged" : true, "insertedId" : 1 }Following is the query to display all documents from a collection with the help of find() method −> db.updateASingleListDemo.find().pretty();This will produce the following output −{ "_id" : 1, "EmployeeName" : "Chris", "EmployeeDetails" : [ { "EmployeeId" : "EMP-101", "EmployeeSalary" : 18999 } ] }Following is the query ...
Read MoreFilter by several array elements in MongoDB?
For this, you can use $elemMatch operator. The $elemMatch operator matches documents that contain an array field with at least one element that matches all the specified query criteria. Let us first create a collection with documents −> db.filterBySeveralElementsDemo.insertOne( "_id":100, "StudentDetails": [ { "StudentName": "John", "StudentCountryName": "US", }, { "StudentName": "Carol", "StudentCountryName": "UK" } ] } ); { "acknowledged" : true, "insertedId" : 100 } > db.filterBySeveralElementsDemo.insertOne( { ...
Read MoreHow to store time created in a MySQL table?
You can use DEFAULT CURRENT_TIMESTAMP. Keep in mind that it will work only at the time of insertion. Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Arrivaltime TIMESTAMP DEFAULT CURRENT_TIMESTAMP ); Query OK, 0 rows affected (0.31 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(Arrivaltime) values('2018-01-31 10:34:56'); Query OK, 1 row affected (0.06 sec) mysql> insert into DemoTable values(); Query OK, 1 row affected (0.06 sec) mysql> insert into DemoTable(Arrivaltime) values('2019-01-31 11:10:12'); Query OK, 1 row affected (0.04 sec)Display ...
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