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Articles by Krantik Chavan
Page 15 of 18
Can I write my own MySQL functions to use in MySQL queries?
Yes, you can write own MySQL function to use in MySQL queries. Following is the syntax:DELIMITER // CREATE FUNCTION yourFunctionName(optional parameters)) RETURNS yourDataType DETERMINISTIC NO SQL BEGIN yourStatements1 . . . . N END // DELIMITER ;We have used the CREATE FUNCTION above to create a custom function.Let us create a custom MySQL function to use in MySQL query:mysql> DELIMITER // mysql> CREATE FUNCTION get_First_Name(Name VARCHAR(255)) RETURNS VARCHAR(255) DETERMINISTIC NO SQL BEGIN RETURN LEFT(Name, LOCATE(' ', Name) - 1); END // Query OK, 0 rows affected (0.20 sec) mysql> DELIMITER ;Now call ...
Read MoreHow to get the seconds and minutes between two Instant timestamps in Java
The following are the two Instant timestamps:Instant one = Instant.ofEpochSecond(1355836728); Instant two = Instant.ofEpochSecond(1355866935);Get the Duration between both the Instant:Duration res = Duration.between(one, two);Now, get the seconds between the two timestamps:long seconds = res.getSeconds();Now, get the minutes between the two timestamps:long minutes = res.abs().toMinutes();Exampleimport java.time.Duration; import java.time.Instant; public class Demo { public static void main(String[] args) { Instant one = Instant.ofEpochSecond(1355836728); Instant two = Instant.ofEpochSecond(1355866935); Duration res = Duration.between(one, two); System.out.println(res); long seconds = res.getSeconds(); System.out.println("Seconds between Durations = "+seconds); ...
Read MoreHow to SELECT records if the absolute value of the difference between two values is greater than a certain number?
To SELECT records if the absolute value of the difference between two values is greater than a certain number, following is the syntax:select *from yourTableName where abs(yourColumnName1-yourColumnName2) >= yourCertainNumber;Let us first create a table:mysql> create table DemoTable ( Number1 int , Number2 int ); Query OK, 0 rows affected (0.59 sec)Following is the query to insert some records in the table using insert command:mysql> insert into DemoTable values(10, 20); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values(100, 200); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values(400, 300); Query OK, 1 ...
Read MoreHow to display only 200 characters from total value in MySQL?
You can use LEFT() from MySQL to display some character from the entire value in MySQL. Following is the syntax:select left(yourColumnName ,200 ) AS anyAliasName from yourTableName;Let us first create a table:mysql> create table DemoTable (Paragraph longtext); Query OK, 0 rows affected (0.71 sec)Following is the query to insert records in the table using insert command:mysql> insert into DemoTable values('Introduction to Java, Introduction to C, Introduction to C++, Introduction to Spring, Introduction to Hibernate, Introduction to Python, Introduction to MySQL, Introduction to MongoDB, Introduction to SQL Server, Introduction to ASP.net, Introduction to JSF'); Query OK, 1 row affected (0.13 sec)Following ...
Read MoreHow to skip blank and null values in MySQL?
To skip blank and null in MySQL, use the following syntax:select *from yourTableName where yourColumnName IS NOT NULL AND yourColumnName '';Let us first create a table:mysql> create table DemoTable (Id int, FirstName varchar(20)); Query OK, 0 rows affected (0.66 sec)Following is the query to insert records in the table using insert command:mysql> insert into DemoTable values(100, 'Larry'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values(101, ''); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable values(102, 'Chris'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable values(103, null); Query OK, 1 ...
Read MoreHow to convert Long array list to long array in Java?
Firstly, declare a Long array list and add some elements to it:ArrayList < Long > arrList = new ArrayList < Long > (); arrList.add(100000 L); arrList.add(200000 L); arrList.add(300000 L); arrList.add(400000 L); arrList.add(500000 L);Now, set the same size for the newly created long array:final long[] arr = new long[arrList.size()]; int index = 0;Each and every element of the Long array list is assigned to the long array:for (final Long value : arrList) { arr[index++] = value; }Exampleimport java.util.ArrayList; public class Demo { public static void main(String[] args) { ArrayList
Read MoreJava Program to convert mathematical string to int
To evaluate mathematical string to int, use Nashorn JavaScript in Java i.e. scripting. Nashorn invoke dynamics feature, introduced in Java 7 to improve performance.For scripting, use the ScriptEngineManager class for the engine:ScriptEngineManager scriptEngineManager = new ScriptEngineManager(); ScriptEngine scriptEngine = scriptEngineManager.getEngineByName("nashorn");Now, use put() to set a key/value pair in the state of the ScriptEngine:scriptEngine.put("one", 10); scriptEngine.put("two", 50); scriptEngine.put("three", 40);Now, here is the mathematical string. Use eval to evaluate:String strExp = "(one + two - three) == 20"; Object evalExp = scriptEngine.eval(strExp);Exampleimport javax.script.ScriptEngine; import javax.script.ScriptEngineManager; import javax.script.ScriptException; public class Demo { public static void main(String[] args) { ScriptEngineManager ...
Read MoreWhat is the most efficient way to check the presence of a row in a MySQL table?
The most efficient want to check the presence of a row, use the count():select count(1) from yourTableName where yourCondition;Let us first create a table:mysql> create table DemoTable ( Id int, FirstName varchar(20) ); Query OK, 0 rows affected (0.73 sec)Following is the query to insert some records in the table using insert command:mysql> insert into DemoTable values(100, 'Larry'); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values(110, 'Sam'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values(120, 'Mike'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values(130, 'Carol'); Query ...
Read MoreHow to update a range of records in MySQL?
To update a range of records in MySQL, you can use BETWEEN. Let us first create a table:mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Name varchar(20), Age int ); Query OK, 0 rows affected (0.53 sec)Following is the query to insert some records in the table using insert command:mysql> insert into DemoTable(Name, Age) values('Larry', 23); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable(Name, Age) values('Sam', 24); Query OK, 1 row affected (0.21 sec) mysql> insert into DemoTable(Name, Age) values('Chris', 21); Query OK, 1 row affected (0.10 sec) mysql> insert ...
Read MoreCan we ignore duplicate rows in COUNT?
Yes, we can ignore duplicate rows in COUNT using DISTINCT. Following is the syntax:select count(distinct yourColumnName) from yourTableName;In MySQL, COUNT() will display the number of rows. DISTINCT is used to ignore duplicate rows and get the count of only unique rows.Let us first create a table:mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FirstName varchar(10) ); Query OK, 0 rows affected (0.47 sec)Following is the query to insert some records in the table using insert command:mysql> insert into DemoTable(FirstName) values('Larry'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable(FirstName) values('John'); Query OK, ...
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