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Articles by Paul Richard
Page 3 of 5
What are MySQL subqueries and its general categories?
A subquery is best defined as a query within a query. Subqueries enable you to write queries that select data rows for criteria that are actually developed while the query is executing at runtime. More formally, it is the use of a SELECT statement inside one of the clauses of another SELECT statement. In fact, a subquery can be contained inside another subquery, which is inside another subquery, and so forth. A subquery can also be nested inside INSERT, UPDATE, and DELETE statements. Subqueries must be enclosed within parentheses.A subquery can be used any place where an expression is allowed ...
Read MoreWhat is the advantage of CONCAT_WS() function over CONCAT() function when we want to concatenate the values from the column and any of the columns have NULL as its value?
As we know that CONCAT() function returns NULL if any of the arguments is NULL but CONCAT_WS() function returns NULL only if the first argument i.e. the separator is NULL and it ignores any other NULL. We can say this is the advantage of CONCAT_WS() function over CONCAT() function when we want to concatenate the values from the column and any of the columns have NULL as its value. To understand it, we consider the example from the table ‘Student_name; which have the following data −mysql> Select * from Student_Name; +---------+-------+---------+ | FName | Mname | Lname ...
Read MoreWhat happens if we provide NULL as an argument to MySQL CHAR() function?
MySQL CHAR() function will ignore NULL if it is provided as an argument to it. To understand it, consider the following examples −mysql> Select CHAR(65,66,67,NULL); +---------------------+ | CHAR(65,66,67,NULL) | +---------------------+ | ABC | +---------------------+ 1 row in set (0.00 sec) mysql> Select CHAR(NULL,66,67,NULL); +-----------------------+ | CHAR(NULL,66,67,NULL) | +-----------------------+ | BC | +-----------------------+ 1 row in set (0.00 sec)In both the examples above, CHAR() function ignores the NULL and converts the numeric value into character value.
Read MoreDouble brace initialization in Java
Double braces can be used to create and initialize objects in a single Java expression. See the example below −Exampleimport java.util.ArrayList; import java.util.List; public class Tester{ public static void main(String args[]) { List list = new ArrayList(); list.add("A"); list.add("B"); list.add("C"); list.add("D"); list.add("E"); list.add("F"); System.out.println(list); List list1 = new ArrayList() { { add("A"); add("B");add("C"); add("D");add("E");add("F"); ...
Read MoreDo we need forward declarations in Java?
Forward declarations means the declaration of a method or variable prior to its implementation. Such declaration is necessary in C/C++ programming language in order to be able to use a variable or object before its implementation. In case, if we want to use a library code, then we need to create its header file and use it. But this is not a case in Java.Java allows using a variable, class prior to its declaration and implementation.Java allows using libraries code without any need of header files.Following example showcases the same. Here we have used a class object before its declaration.Examplepublic ...
Read MoreHow can we stuff a string with another one using MySQL functions?
MySQL have two functions namely LPAD() and RPAD() with the help of which we can stuff a string with another string.LPAD() function, as the name suggests, left stuff a string with another string. Following is the syntax for using it in MySQL −SyntaxLPAD(original_string, @length, pad_string)Here, original_string is the string in which we stuff another string.@length is the total length of string returned after stuffing.Pad_string is the string which is to be stuffed with original_string.Examplemysql> SELECT LPAD('tutorialspoint', 18, 'www.'); +----------------------------------+ | LPAD('tutorialspoint', 18, 'www.') | +----------------------------------+ | www.tutorialspoint | +----------------------------------+ 1 row in set ...
Read MoreHow can I use RAND() function in an ORDER BY clause to shuffle MySQL set of rows?
When we use MySQL ORDER BY clause with RAND() function then the result set would have the shuffled set of rows. In other words, the result set would be in a random order. To understand it considers a table ‘Employee’ having the following records −mysql> Select * from employee; +----+--------+--------+ | ID | Name | Salary | +----+--------+--------+ | 1 | Gaurav | 50000 | | 2 | Rahul | 20000 | | 3 | Advik | 25000 | | 4 | Aarav | 65000 | | ...
Read MoreHow can I define a column of a MySQL table PRIMARY KEY without using the PRIMARY KEY keyword?
As we know that a PRIMARY KEY column must have unique values and cannot have null values hence if we will define a column with UNIQUE and NOT NULL constraint both then that column would become PRIMARY KEY column.ExampleIn this example, we have created a table ‘Student123’ by defining column ‘RollNo’ with UNIQUE and NOT NULL constraints. Now, by describing the table we can see that ‘RollNo’ is the PRIMARY KEY column.mysql> Create table Student123(RollNo INT UNIQUE NOT NULL, Name varchar(20)); Query OK, 0 rows affected (0.25 sec) mysql> DESCRIBE Student123; +--------+-------------+------+-----+---------+-------+ | Field | Type ...
Read MoreExponential Search
Exponential search is also known as doubling or galloping search. This mechanism is used to find the range where the search key may present. If L and U are the upper and lower bound of the list, then L and U both are the power of 2. For the last section, the U is the last position of the list. For that reason, it is known as exponential.After finding the specific range, it uses the binary search technique to find the exact location of the search key.The complexity of Exponential Search TechniqueTime Complexity: O(1) for the best case. O(log2 i) ...
Read MoreJava Conversions and Promotions
We can convert one data types into another data type using casting. Narrowing ConversionNarrowing refers to passing a higher size data type like int to a lower size data type like short. It may lead to data loss. Following program output will be 44.public class MyFirstJavaProgram { public static void main(String []args) { int a = 300; byte b = (byte)a; // narrowing System.out.println(b); } }Widening/Promotion ConversionWidening refers to passing a lower size data type like ...
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