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Articles by Vikyath Ram
Page 7 of 10
What MySQL returns if the search string, provided in FIELD() function, is NULL?
As we know that NULL fails equality comparison with any value hence if the search string, provided in FIELD() function, is NULL then MySQL returns 0 as output.Examplemysql> Select FIELD(NULL,'Ram','is','good','boy'); +-------------------------------------+ | FIELD(NULL,'Ram','is','good','boy') | +-------------------------------------+ | 0 | +-------------------------------------+ 1 row in set (0.00 sec)
Read MoreHow can we emulate CHECK CONSTRAINT by using views?
As we know that MySQL supports foreign key for referential integrity but it does not support CHECK constraint. But we can emulate them by using triggers. It can be illustrated with the help of an example given below −ExampleSuppose we have a table named ‘car1’ which can have the fix syntax registration number like two letters, a dash, three digits, a dash, two letters as follows −mysql> Create table car1 (number char(9)); Query OK, 0 rows affected (0.32 sec) mysql> Insert into car1 values('AB-235-YZ'); Query OK, 1 row affected (0.10 sec)The above value is a valid one but what ...
Read MoreHow can we apply the PRIMARY KEY constraint to the field of an existing MySQL table?
We can apply the PRIMARY KEY constraint to a column of an existing MySQL table with the help of ALTER TABLE statement. SyntaxALTER TABLE table_name MODIFY colum_name datatype PRIMARY KEY; OR ALTER TABLE table_name ADD PRIMARY KEY (colum_name); Suppose we have the following table named ‘Player’ and we want to add the PRIMARY KEY constraint to the column ‘ID’ then it can be done with the help of ALTER TABLE command as follows −mysql> DESCRIBE Player; +-------+-------------+------+-----+---------+-------+ | Field | Type ...
Read MoreJava labelled for loop
Following program is using labeled for loops. Example public class Tester { public static void main(String args[]) { first: for (int i = 0; i
Read MoreDoes a favicon have to be 32x32 or 16x16?
A favicon is a little icon visible on the web browser tab, just before the page title. It is generally a logo with a smaller size. The size of a favicon is 16x16, since it also gets displayed next to the URL of your site in a browser's address bar.The 16x16 size for Favicon is suitable for web browsers. But the size varies on multiple platforms and devices. The size is added using the sizes attribute.The preferred size, 1.16x16: For web browser 2. 32x32: or taskbar shortcut icon 3. 96x96: For desktop shortcut iconHere’s how you can add them ...
Read MoreMember variables vs Local variables in Java
Local VariableLocal variables are declared in methods, constructors, or blocks.Local variables are created when the method, constructor or block is entered and the variable will be destroyed once it exits the method, constructor, or block.Access modifiers cannot be used for local variables.Local variables are visible only within the declared method, constructor, or block.Local variables are implemented at stack level internally.There is no default value for local variables, so local variables should be declared and an initial value should be assigned before the first use.Instance/Member VariableInstance variables are declared in a class, but outside a method, constructor or any block.When a ...
Read MoreHow do you check if a ResultSet is empty or not in JDBC?
Whenever we execute SQL statements using the executeQuery() method, it returns a ResultSet object which holds the tabular data returned by the SELECT queries(in general).The ResultSet object contains a cursor/pointer which points to the current row. Initially this cursor is positioned before first row (default position).The next() methodThe next() method of the ResultSet interface moves the pointer of the current (ResultSet) object to the next row, from the current position.This method returns a boolean value specifying whether the ResultSet object contains more rows. If there are no rows next to its current position this method returns false, else it returns true.Therefore, ...
Read MoreHow to count the number characters in a Java string?
Declare an integer, initialize it with 0, in for loop increment it for each character. Example public class Sample { public static void main(String args[]) { String str = new String("Hi welcome to Tutorialspoint"); int count = 0; for(int i = 0; i<str.length(); i++) { count++; } System.out.println("Number characters in the given string (including spaces) "+count); } } Output Number characters in the given string (including spaces) 28
Read MoreIn case of FOREIGN KEY constraint, what kind of relationship is there between MySQL parent and child tables?
The relationship between parent and child table is One-to-Many relationship. It can be understood with the example of two tables named ‘customer’ and ‘orders’. Here, ‘customer’ is the parent table and ‘orders’ is the child table. The relationship is one-to—many because a customer can have more than one order. It can be demonstrated by inserting the values in both the tables as follows −mysql> Select * from Customer; +----+---------+ | id | name | +----+---------+ | 1 | Gaurav | | 2 | Raman | | 3 | Harshit | | 4 | Aarav | +----+---------+ ...
Read MoreThe ResultSet updateRow() method with example
When we execute certain SQL queries (SELECT query in general) they return tabular data.The java.sql.ResultSet interface represents such tabular data returned by the SQL statements.i.e. the ResultSet object holds the tabular data returned by the methods that execute the statements which quires the database (executeQuery() method of the Statement interface in general).The ResultSet object has a cursor/pointer which points to the current row. Initially this cursor is positioned before first row.The updateRow() method of the ResultSet interface updates the contents of the current row to the database. For example if we have updated the values of a particular record using the updateXXX() ...
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