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The summaryStatistics() method of the DoubleStream class returns a DoubleSummaryStatistics describing various summary data about the elements of this stream. This is a special case of a reduction.The syntax is as followsDoubleSummaryStatistics summaryStatistics()Here, DoubleSummaryStatistics is a state object for collecting statistics such as count, min, max, average, etc. It works with streams. To use the DoubleStream class in Java, import the following packageimport java.util.stream.DoubleStream;First, create a DoubleStream and add some elementsDoubleStream doubleStream = DoubleStream.of(20.5, 35.8, 45.9, 50.8, 80.7);Now, get the statisticsDoubleSummaryStatistics details = doubleStream.summaryStatistics();The following is an example to implement DoubleStream summaryStatistics() methodExample Live Demoimport java.util.stream.DoubleStream; import java.util.DoubleSummaryStatistics; public class Demo ... Read More
You can add/set an auto increment constraint to a column in a table using the ALTER TABLE command.SyntaxALTER TABLE table_name ADD id INT PRIMARY KEY AUTO_INCREMENTAssume we have a table named Dispatches in the database with 7 columns namely id, CustomerName, DispatchDate, DeliveryTime, Price and, Location with description as shown below:+--------------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------------+--------------+------+-----+---------+-------+ | ProductName | varchar(255) | YES | UNI | NULL | | | CustomerName | varchar(255) | YES | ... Read More
Following is the syntax to return only a single property _id in MongoDBdb.yourCollectionName.find({}, {"_id": 1}).pretty();Let us first create a collection with documents> db.singlePropertyIdDemo.insertOne({"_id":101, "UserName":"Larry", "UserAge":21}); { "acknowledged" : true, "insertedId" : 101 } > db.singlePropertyIdDemo.insertOne({"_id":102, "UserName":"Mike", "UserAge":26}); { "acknowledged" : true, "insertedId" : 102 } > db.singlePropertyIdDemo.insertOne({"_id":103, "UserName":"Chris", "UserAge":24}); { "acknowledged" : true, "insertedId" : 103 } > db.singlePropertyIdDemo.insertOne({"_id":104, "UserName":"Robert", "UserAge":23}); { "acknowledged" : true, "insertedId" : 104 } > db.singlePropertyIdDemo.insertOne({"_id":105, "UserName":"John", "UserAge":27}); { "acknowledged" : true, "insertedId" : 105 }Following is the query to display all documents from a collection with the help of find() method> db.singlePropertyIdDemo.find().pretty();This will produce ... Read More
You can use the concept of toArray() to create array. Following is the syntax −db.yourCollectonName.find({}, {yourFieldName:1}).toArray();Let us create a collection with documents −> db.createArrayDemo.insertOne({"UserName":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5cbd6461de8cc557214c0e00") } > db.createArrayDemo.insertOne({"UserName":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5cbd6467de8cc557214c0e01") } > db.createArrayDemo.insertOne({"UserName":"Robert"}); { "acknowledged" : true, "insertedId" : ObjectId("5cbd646cde8cc557214c0e02") } > db.createArrayDemo.insertOne({"UserName":"Sam"}); { "acknowledged" : true, "insertedId" : ObjectId("5cbd6470de8cc557214c0e03") }Display all documents from a collection with the help of find() method −> db.createArrayDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5cbd6461de8cc557214c0e00"), "UserName" : "Chris" } { "_id" : ObjectId("5cbd6467de8cc557214c0e01"), ... Read More
There is no equivalent of ROW_NUMBER() in MySQL for inserting but you can achieve this with the help of variable. The syntax is as follows −SELECT (@yourVariableName:=@yourVariableName + 1) AS `anyAliasName`, yourColumnName1, yourColumnName2, ...N FROM yourTableName ,(SELECT @yourVariableName:=0) AS anyAliasName;To understand the above syntax, let us create a table. The query to create a table is as follows −mysql> create table RowNumberDemo -> ( -> UserId int, -> UserName varchar(20) -> ); Query OK, 0 rows affected (0.74 sec)Insert some records in the table using insert command. The ... Read More
You can use UNION to get the previous and next record in MySQL.The syntax is as follows(select *from yourTableName WHERE yourIdColumnName > yourValue ORDER BY yourIdColumnName ASC LIMIT 1) UNION (select *from yourTableName WHERE yourIdColumnName < yourValue ORDER BY yourIdColumnName DESC LIMIT 1);To understand the concept, let us create a table. The query to create a table is as followsmysql> create table previousAndNextRecordDemo - > ( - > Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, - > Name varchar(30) - > ); Query OK, 0 rows affected (1.04 ... Read More
The range of values for a field can be obtained using the range() method in the Instant class in Java. This method requires a single parameter i.e. the ChronoField for which the range of values are required and it returns the range of valid values for the ChronoField.A program that demonstrates this is given as follows −Example Live Demoimport java.time.*; import java.time.temporal.ChronoField; import java.time.temporal.ValueRange; public class Demo { public static void main(String[] args) { Instant i = Instant.now(); ValueRange range1 = i.range(ChronoField.MILLI_OF_SECOND); ... Read More
You can use IN operator for this.The syntax is as follows −SELECT *FROM yourTableName WHERE yourColumnName IN(‘yourValue1’, ‘yourValue2’, ‘yourValue3’, ...........N);To understand the above syntax, let us create a table. The query to create a table is as follows −mysql> create table InOperatorDemo -> ( -> ClientId int -> ); Query OK, 0 rows affected (0.52 sec)Insert some records in the table using insert command. The query is as follows −mysql> insert into InOperatorDemo values(101); Query OK, 1 row affected (0.19 sec) mysql> insert into InOperatorDemo values(110); Query OK, 1 row affected (0.11 sec) mysql> insert into InOperatorDemo ... Read More
Following is the syntax to count the number of documents in a MongoDB collectionlet anyVariableName= db.getCollection(‘yourCollectionName’); yourVariableName.count();Let us first create a collection with documents> db.countNumberOfDocumentsDemo.insertOne({"CustomerName":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5c9a5e2015e86fd1496b38a1") } >db.countNumberOfDocumentsDemo.insertOne({"CustomerName":"Ramit", "CustomerAge":23}); { "acknowledged" : true, "insertedId" : ObjectId("5c9a5e3515e86fd1496b38a2") } >db.countNumberOfDocumentsDemo.insertOne({"CustomerName":"Adam", "CustomerAge":27, "CustomerCountryName":"US"}); { "acknowledged" : true, "insertedId" : ObjectId("5c9a5e4c15e86fd1496b38a3") }Following is the query to display all documents from a collection with the help of find() method> db.countNumberOfDocumentsDemo.find().pretty();This will produce the following output{ "_id" : ObjectId("5c9a5e2015e86fd1496b38a1"), "CustomerName" : "Bob" } { "_id" : ObjectId("5c9a5e3515e86fd1496b38a2"), "CustomerName" : "Ramit", "CustomerAge" ... Read More
To save new Date() in MongoDB, you can use new ISODate(). Let us create a collection with documents −> db.saveDateDemo.insertOne({"UserName":"John", "UserLoginDatetime":new ISODate('2018-01-31 12:34:56')}); { "acknowledged" : true, "insertedId" : ObjectId("5cbd67d4de8cc557214c0e04") } > db.saveDateDemo.insertOne({"UserName":"John", "UserLoginDatetime":new ISODate('2019-02-01 04:01:10')}); { "acknowledged" : true, "insertedId" : ObjectId("5cbd67e8de8cc557214c0e05") } > db.saveDateDemo.insertOne({"UserName":"John", "UserLoginDatetime":new ISODate('2019-04-22 12:36:45')}); { "acknowledged" : true, "insertedId" : ObjectId("5cbd6805de8cc557214c0e06") }Display all documents from a collection with the help of find() method −> db.saveDateDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5cbd67d4de8cc557214c0e04"), "UserName" : "John", "UserLoginDatetime" : ISODate("2018-01-31T12:34:56Z") } { "_id" : ObjectId("5cbd67e8de8cc557214c0e05"), ... Read More