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Articles by Kumar Varma
Page 5 of 9
How can we use ORDER BY clause while calculating the Date?
It would be more convenient to find a record if we will use ORDER BY clause while calculating the date. To understand it, we have the data from table ‘Collegedetail’ as follows −mysql> Select * from Collegedetail; +------+---------+------------+ | ID | Country | Estb | +------+---------+------------+ | 111 | INDIA | 2010-05-01 | | 130 | INDIA | 1995-10-25 | | 139 | USA | 1994-09-25 | | 1539 | UK | 2001-07-23 | | 1545 ...
Read MoreHow can we check for NULL in a MySQL query?
With the help of IS NULL operator, we can check for NULL in a MySQL query. We cannot use = (comparison operator) because as we know that NULL is not a value. Following example using the data from ‘employee’ table will exhibit it −Examplemysql> Select * from Employee WHERE Salary IS NULL; +----+-------+--------+ | ID | Name | Salary | +----+-------+--------+ | 7 | Aryan | NULL | | 8 | Vinay | NULL | +----+-------+--------+ 2 rows in set (0.00 sec)The query above use IS NULL operator and produces the output where salary column is having NULL.mysql> ...
Read MoreWhat MySQL returns if sub-query, used to assign new values in the SET clause of UPDATE statement, returns no rows?
In this case, MySQL will provide a NULL value to the SET clause. Following example will demonstrate it −Examplemysql> Select * from student; +----+---------+-----------+ | Id | Name | grade | +----+---------+-----------+ | 1 | Rahul | Good | | 2 | Gaurav | Good | | 3 | Raman | Excellent | | 4 | Harshit | Average | | 5 | Aarav | Best | | 6 | Ram | average | +----+---------+-----------+ 6 rows in set (0.00 sec) ...
Read MoreHow can I insert the values in columns without specifying the names of the column in MySQL INSERT INTO statement?
For inserting the values in the column without specifying the names of the columns in INSERT INTO statement, we must give the number of values that matches the number of columns in the table along with taking care about the data type of that column too.ExampleIn the example below we have inserted the values without specifying the name of the column.mysql> Insert into student values(100, 'Gaurav', 'Ph.D'); Query OK, 1 row affected (0.08 sec) mysql> Select * from student; +--------+--------+--------+ | RollNO | Name | Class | +--------+--------+--------+ | 100 | Gaurav | Ph.D | +--------+--------+--------+ ...
Read MoreHow to insert NULL keyword as a value in a character type column of MySQL table having NOT NULL constraint?
It is quite possible to insert the NULL keyword as a value in a character type column having NOT NULL constraint because NULL is a value in itself. Following example will exhibit it −ExampleSuppose we have a table test2 having character type column ‘Name’ along with NOT NULL constraint on it. It can be checked from the DESCRIBE statement as follows −mysql> Describe test2\G *************************** 1. row *************************** Field: id Type: int(11) Null: NO Key: Default: NULL Extra: *************************** 2. row *************************** Field: NAME Type: varchar(20) Null: NO Key: ...
Read MoreJava (JVM) Memory Types
Java Virtual Machine is a program/software which takes Java bytecode (.class files)and converts the byte code (line by line) into machine understandable code.JVM contains a module known as a class loader. A class loader in JVM loads, links and, initializes a program. It−Loads the class into the memory. Verifies the byte code instructions.Allocates memory for the program.The memory in the JVM is divided into five different parts namely− Method area− The method area stores the class code − code of the variables and methods. Heap − The Java objects are created in this area. Java Stack− While running methods the results are stored in ...
Read MoreJava labelled statement
Yes. Java supports labeled statements. You can put a label before a for statement and use the break/continue controls to jump to that label. Example See the example below. public class Tester { public static void main(String args[]) { first: for (int i = 0; i
Read MoreHow to create a subarray from another array in Java
Use Arrays.copyOfRange() method to get a subarray.Exampleimport java.util.Arrays; public class Tester { public static void main(String[] args) { int[] array = new int[] {1, 2, 3, 4, 5}; int[] subArray = Arrays.copyOfRange(array, 0, 2); System.out.println("Array: "); for(int i = 0; i < array.length; i++) { System.out.print(array[i] + " "); } System.out.println("Sub array: "); for(int i = 0; i < subArray.length; i++) { System.out.print(subArray[i] + " "); } } }OutputArray: 1 2 3 4 5 Sub array: 1 2
Read MoreIs there any way to use values from a JSON object in a MySQL Select statement?
Yes, you can use json_extract(). Let us first create a table −mysql> create table DemoTable -> ( -> Data json -> ); Query OK, 0 rows affected (0.63 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('{"Name": "John", "CountryName": "US"}'); Query OK, 1 row affected (0.33 sec) mysql> insert into DemoTable values('{"Name": "Chris", "CountryName": "UK"}'); Query OK, 1 row affected (0.15 sec)Display all records from the table using select statement −mysql> select *from DemoTable;Output+----------------------------------------+ | Data ...
Read MoreSTR_TO_DATE as column, but column not found?
You can use having clause. Let us first create a table −mysql> create table DemoTable -> ( -> AdmissionDate varchar(100) -> ); Query OK, 0 rows affected (0.55 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('10/12/2017'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values('01/11/2018'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values('31/01/2019'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values('09/06/2019'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable values('19/04/2019'); Query OK, 1 ...
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