Article Categories
- All Categories
-
Data Structure
-
Networking
-
RDBMS
-
Operating System
-
Java
-
MS Excel
-
iOS
-
HTML
-
CSS
-
Android
-
Python
-
C Programming
-
C++
-
C#
-
MongoDB
-
MySQL
-
Javascript
-
PHP
Articles by Chandu yadav
Page 65 of 81
Get the array of _id in MongoDB?
The _id in MongoDB is a field, which is mandatory. In MongoDB, each document stored in a collection requires a unique _id field that acts as a primary key. Following is the syntax to get the array of all the ids i.e. _id in MongoDBdb.yourCollectionName.find({ _id : { $in : [yourValue1, yourValue2, yourValue3, .......N] } } );Let us first implement the following query to create a collection with documents> db.selectInWhereIdDemo.insertOne({"_id":23}); { "acknowledged" : true, "insertedId" : 23 } > db.selectInWhereIdDemo.insertOne({"_id":28}); { "acknowledged" : true, "insertedId" : 28 } > db.selectInWhereIdDemo.insertOne({"_id":45}); { "acknowledged" : true, "insertedId" : 45 } > db.selectInWhereIdDemo.insertOne({"_id":75}); ...
Read MoreGeneration of triangular wave using DAC interface
We write an 8085 assembly language program for the generation of triangular waveform using the Digital to Analog Converter (DAC) interface. The display of the waveform is seen on the CRO.Let us consider a problem solution in this domain. The problem states that: To get unipolar output, J1 is shorted to J2 on the interface. To display the waveform on a CRO, connect pin 1 of connector P1 to CRO signal pin, and pin 2 of connector P1 to CRO ground pin.Program; FILE NAME DAC_TO_TRIANG.ASM ORG C100H X DW 00FFH ; the fall of rise and time I proportional directly to ...
Read MoreCheck how many rows are in a MySQL database table?
To know how many rows are in a ySQL database table, you need to use aggregate function COUNT(*).The syntax is as followsSELECT COUNT(*) FROM yourTableName;To understand the above syntax, let us create a table. The query to create a table is as followsmysql> create table CountRowsDemo - > ( - > Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, - > Name varchar(20) - > ); Query OK, 0 rows affected (0.78 sec)Insert some records in the table using insert command.The query is as followsmysql> insert into CountRowsDemo(Name) values(NULL); Query OK, 1 row affected (0.15 sec) mysql> ...
Read MoreSearch a string with special characters in a MongoDB document?
To search a string with special characters in MongoDB document, you can use \. Here, we have special character $ in our string.Let us first implement the following query to create a collection with documents>db.searchDocumentWithSpecialCharactersDemo.insertOne({"UserId":"Smith$John123", "UserFirstName":"John", "UserLastName":"Smith"}); { "acknowledged" : true, "insertedId" : ObjectId("5c987b98330fd0aa0d2fe4b1") } >db.searchDocumentWithSpecialCharactersDemo.insertOne({"UserId":"Taylor$Carol983", "UserFirstName":"Carol", "UserLastName":"Taylor"}); { "acknowledged" : true, "insertedId" : ObjectId("5c987bdb330fd0aa0d2fe4b2") } >db.searchDocumentWithSpecialCharactersDemo.insertOne({"UserId":"Doe$John999", "UserFirstName":"John", "UserLastName":"Doe"}); { "acknowledged" : true, "insertedId" : ObjectId("5c987bee330fd0aa0d2fe4b3") } >db.searchDocumentWithSpecialCharactersDemo.insertOne({"UserId":"Miller$David555", "UserFirstName":"David", "UserLastName":"Miller"}); { "acknowledged" : true, "insertedId" : ObjectId("5c987c01330fd0aa0d2fe4b4") }Following is the query to display all documents from a collection with the help of ...
Read MoreHow to add a “created at” column in a table to set the timestamp in MySQL?
You need to use ALTER command to add a created at column to an already created table in MySQL.Let us first create a table. The query to create a table is as follows. Here is your table without the “created at” columnmysql> create table formDemo - > ( - > Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, - > Email varchar(128), - > PhoneNumber varchar(15), - > Country varchar(30), - > Platform varchar(40) - > ); Query OK, 0 ...
Read MoreHow to get all the collections from all the MongoDB databases?
To get all the collections from all the databases, let us first get all the databases using the following query> switchDatabaseAdmin = db.getSiblingDB("admin"); admin > allDatabaseName = switchDatabaseAdmin.runCommand({ "listDatabases": 1 }).databases;This will produce the following output[ { "name" : "admin", "sizeOnDisk" : 495616, "empty" : false }, { "name" : "config", "sizeOnDisk" : 98304, "empty" : false }, { "name" : "local", "sizeOnDisk" : 73728, "empty" : false ...
Read MoreChange a MySQL Column datatype from text to timestamp?
To change a MySQL column datatype from text to timestamp, you need to use ALTER command.The syntax is as followsALTER TABLE yourTableName MODIFY COLUMN yourColumnName TIMESTAMP;To understand the above syntax, let us create a table.The query to create a table is as followsmysql> create table textTotimestampdemo - > ( - > Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, - > Source text - > ); Query OK, 0 rows affected (0.44 sec)Here is the description of table using DESC command.The syntax is as followsDESC yourTableName;The query is as followsmysql> desc textTotimestampdemo;The following is the output+--------+---------+------+-----+---------+----------------+ | ...
Read MoreSearch for a text in MongoDBs Double Nested Array?
Search for a text in MongoDBs Double Nested Array with the help of dot(.) notation. Let us first create a collection. Following is the query to create a collection with documents> db.doubleNestedArrayDemo.insertOne( ... { ... "StudentId" : "1000", ... "StudentName" : "Larry", ... "StudentDetails" : [ ... { ... "ProjectName" : "Online Banking", ... "ProjectDetails" : [ ... { ... ...
Read MoreHow to get default device sdk version in android?
This example demonstrate about How to get default device sdk version in android.Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.Step 2 − Add the following code to res/layout/activity_main.xml. In the above code, we have taken text view to show device sdk version.Step 3 − Add the following code to java/MainActivity.xmlpackage com.example.myapplication; import android.Manifest; import android.content.Context; import android.content.pm.PackageManager; import android.os.Build; import android.os.Bundle; import android.support.annotation.NonNull; import android.support.annotation.RequiresApi; import android.support.v4.app.ActivityCompat; import android.support.v7.app.AppCompatActivity; import android.telephony.TelephonyManager; import android.widget.TextView; import static android.Manifest.permission.READ_PHONE_NUMBERS; import ...
Read MoreCan we exclude entries with “0” while using MySQL AVG function?
To exclude entries with “0”, you need to use NULLIF() with function AVG().The syntax is as followsSELECT AVG(NULLIF(yourColumnName, 0)) AS anyAliasName FROM yourTableName;Let us first create a tablemysql> create table AverageDemo - > ( - > Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, - > StudentName varchar(20), - > StudentMarks int - > ); Query OK, 0 rows affected (0.72 sec)Insert some records in the table using insert command.The query is as followsmysql> insert into AverageDemo(StudentName, StudentMarks) values('Adam', NULL); Query OK, 1 row affected (0.12 sec) mysql> insert into AverageDemo(StudentName, StudentMarks) values('Larry', 23); Query OK, ...
Read More