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Articles by Nishtha Thakur
Page 31 of 40
How to form a composite key to be unique in MySQL?
To form a composite key to be unique, you need to use ADD UNIQUE command. Following is the syntax −alter table yourTableName add unique yourUniqueName( yourColumnName1, yourColumnName2, .......N);Let us first create a table. Following is the query −mysql> create table makeCompositeKeyDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> StudentName varchar(40), -> StudentAge int, -> StudentGrade char(1) -> ); Query OK, 0 rows affected (2.34 sec)Now check the description of the table using DESC command. Following is the query −mysql> desc makeCompositeKeyDemo;This will produce the following output −+--------------+-------------+------+-----+---------+----------------+ | Field ...
Read MoreIdentify last document from MongoDB find() result set?
To identify the last document from MongoDB find() result set, you can use sort() in descending order. The syntax is as follows −db.yourCollectionName.find().sort( { _id : -1 } ).limit(1).pretty();To understand the above syntax, let us create a collection with the document. The query to create a collection with a document is as follows −> db.identifyLastDocuementDemo.insertOne({"UserName":"Larry", "UserAge":24, "UserCountryName":"US"}); { "acknowledged" : true, "insertedId" : ObjectId("5c94a2ff4cf1f7a64fa4df57") } > db.identifyLastDocuementDemo.insertOne({"UserName":"Chris", "UserAge":21, "UserCountryName":"UK"}); { "acknowledged" : true, "insertedId" : ObjectId("5c94a3094cf1f7a64fa4df58") } > db.identifyLastDocuementDemo.insertOne({"UserName":"David", "UserAge":25, "UserCountryName":"AUS"}); { "acknowledged" : true, "insertedId" : ObjectId("5c94a3174cf1f7a64fa4df59") } > db.identifyLastDocuementDemo.insertOne({"UserName":"Sam", "UserAge":26, "UserCountryName":"US"}); { ...
Read MoreHow to use Navigable set interface in Android?
This example demonstrates about How to use Navigable set interface in AndroidStep 1 &minus 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 the name and record number as Edit text, when the user clicks on save button it will store the data into ArrayList. Click on the refresh button to get ...
Read MoreHow to use replace command in Android sqlite?
Before getting into example, we should know what sqlite data base in android is. SQLite is an open source SQL database that stores data to a text file on a device. Android comes in with built in SQLite database implementation. SQLite supports all the relational database features. In order to access this database, you don't need to establish any kind of connections for it like JDBC, ODBC etc.This example demonstrate about How to use replace command in Android sqlite.Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to ...
Read MoreHow to use charAt() in Android textview?
This example demonstrates about How to use charAt() in Android text view.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 the name as Edit text, when user clicks on the button it will take data and find 5th character.Step 3 − Add the following code to src/MainActivity.javapackage com.example.myapplication; import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.view.View; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; ...
Read MoreHow to use Tree set in Android?
This example demonstrates about How to use Tree set in AndroidStep 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 the name and record number as Edit text, when the user clicks on save button it will store the data into ArrayList. Click on the refresh button to get the ...
Read MoreHow to get day of month, day of year and day of week in android using offset date time API class?
This example demonstrate about How to get day of month, day of year and day of week in android using offset date time API class.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 textview to show day of month, day of year and day of the week.Step 3 − Add the following code to src/MainActivity.javapackage com.example.myapplication; import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.widget.TextView; import ...
Read MoreFind items that do not have a certain field in MongoDB?
To find items that do not have a certain field, use the $exists operator. The syntax is as follows −> db.yourCollectionName.find({"yourItemName":{$exists:false}}).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.findDocumentDoNotHaveCertainFields.insertOne({"UserId":101, "UserName":"John", "UserAge":21}); { "acknowledged" : true, "insertedId" : ObjectId("5c8a95fb6cea1f28b7aa07fb") } > db.findDocumentDoNotHaveCertainFields.insertOne({"UserName":"David", "UserAge":22, "UserFavouriteSubject":["C", "Java"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c8a96116cea1f28b7aa07fc") } > db.findDocumentDoNotHaveCertainFields.insertOne({"UserName":"Bob", "UserAge":24, "UserFavouriteSubject":["MongoDB", "MySQL"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c8a96306cea1f28b7aa07fd") }Display all documents from a collection with the help of find() method. The ...
Read MoreHow to SELECT min and max value from the part of a table in MySQL?
To select min and max value from the part of a table in MySQL, use the following syntax −select min(yourColumnName) as yourAliasName1, max(yourColumnName) as yourAliasName2 from (select yourColumnName from yourTableName limit yourLimitValue) tbl1;Let us first create a table. Following is the query −mysql> create table MinAndMaxValueDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Value int -> ); Query OK, 0 rows affected (0.52 sec)Insert records in the table using insert command. Following is the query −mysql> insert into MinAndMaxValueDemo(Value) values(10); Query OK, 1 row affected (0.16 sec) mysql> insert into MinAndMaxValueDemo(Value) ...
Read MoreLoop through all MongoDB collections and execute query?
First of all, you need to get your collection with the help of getCollectionNames().The database name is “test”. Let us loop through all MongoDB collections and execute the query. The query is as follows −> db.getCollectionNames().forEach(function(collectioNameDemo) ... { ... var nextDemo = db[(collectioNameDemo) ].find().sort({_id:-1}).limit(1); ... if (nextDemo.hasNext()) ... { ... printjson(nextDemo.next()._id.getTimestamp()); ... } ... });The following is the output −ISODate("2019-02-21T18:52:43Z") ISODate("2019-03-19T17:49:00Z") ISODate("2019-03-06T15:40:12Z") ISODate("2019-03-15T16:31:50Z") ISODate("2019-02-21T15:40:52Z") ISODate("2019-03-06T06:14:37Z") ISODate("2019-02-21T19:29:15Z") ISODate("2019-03-15T13:35:33Z") ISODate("2019-03-14T21:13:58Z") ISODate("2019-03-18T22:02:54Z") ISODate("2019-03-22T18:01:45Z") ISODate("2019-03-06T16:21:14Z") ISODate("2019-02-20T15:04:32Z") ISODate("2019-03-06T07:45:42Z") ISODate("2019-03-19T12:33:17Z") ISODate("2019-03-20T21:39:21Z") ISODate("2019-03-15T16:44:26Z") ISODate("2019-03-22T06:20:45Z") ISODate("2019-02-21T16:40:55Z") ISODate("2019-02-21T12:45:20Z") ISODate("2019-03-06T16:05:48Z") ISODate("2019-03-06T16:00:08Z") ISODate("2019-02-28T12:43:56Z") ISODate("2019-03-20T22:11:41Z") ISODate("2019-03-06T05:56:45Z") ISODate("2019-03-06T07:34:12Z") ISODate("2019-03-14T21:00:16Z") ISODate("2019-02-28T10:33:39Z") ISODate("2019-03-06T05:11:10Z") ISODate("2019-02-28T09:44:28Z") ISODate("2019-03-06T10:13:22Z") ISODate("2019-03-17T21:35:26Z")
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