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Articles by varun
Page 5 of 7
What are static members of a Java class?
In Java, static members are those which belongs to the class and you can access these members without instantiating the class. The static keyword can be used with methods, fields, classes (inner/nested), blocks. Static Methods − You can create a static method by using the keyword static. Static methods can access only static fields, methods. To access static methods there is no need to instantiate the class, you can do it just using the class name as − Example public class MyClass { public static void sample(){ System.out.println("Hello"); ...
Read MoreHow can we use MySQL REPLACE statement to prevent of insertion of duplicate data?
We can use the REPLACE statement while inserting the data to prevent the insertion of duplicate data. If we will use the REPLACE command rather than the INSERT command then if the record is new, it is inserted just as with INSERT else if it is a duplicate, the new record replaces the old one.SyntaxREPLACE INTO table_name(…)Here, table_name is the name of the table in which we want to insert the values.ExampleIn this example we will insert the data with the help of REPLACE statement as follows −mysql> REPLACE INTO person_tbl (last_name, first_name) -> VALUES( 'Ajay', 'Kumar'); Query OK, ...
Read MoreWhy is it necessary to declare NOT FOUND handler while using MySQL cursor?
We must have to declare NOT FOUND handler while working with MySQL cursor because it handles the situation when cursor could not find any row. It also handles the situation when the cursor reaches the end of the row because every time we call FETCH statement the cursor finds to attempt the next row in the result set. Following is the syntax to declare NOT FOUND handler −DECLARE CONTINUE HANDLER FOR NOT FOUND SET var_name = value;Here var_name is the name of any variable and value would be the value of that variable. For example, we can declare it as ...
Read MoreHow can local variables be used in MySQL stored procedure?
Local variables are those variables that are declared within the stored procedure. They are only valid within the BEGIN…END block where they are declared and can have any SQL data type. To demonstrate it, we are creating the following procedure −mysql> DELIMITER // ; mysql> Create Procedure Proc_Localvariables() -> BEGIN -> DECLARE X INT DEFAULT 100; -> DECLARE Y INT; -> DECLARE Z INT; -> DECLARE A INT; -> SET Y = 250; -> SET Z = 200; ...
Read MoreHow can I get the list of columns from a table in the other database than we are currently using?
It can be done with the SHOW COLUMNS statement. Its Syntax would be as follows −SyntaxSHOW COLUMNS FROM db_name.tab_nameHere, tab_name is the name of the table from which we want to see the list of columns.Db_name is the name of the database, in which the table is storedExampleIn the example we are currently using the database ‘query’ and getting the list of columns from table named ‘arena’ stored in mysql ‘database’ −mysql> SHOW COLUMNS FROM mysql.arena\G *************************** 1. row *************************** Field: id Type: int(10) unsigned zerofill Null: NO Key: PRI Default: NULL Extra: auto_increment ...
Read MoreIn MySQL, how can we maintain data-driven table relationship using joins?
Actually, sometimes we can avoid data-driven relationships in tables and we need to join them. It can be done with the help of CASE statement in the SELECT list to handle the joining possibilities. To understand it, we are taking the example of three data-driven tables namely ‘Student_Detail’ which have the following data −mysql> Select * from student_detail; +----+---------+ | Id | Name | +----+---------+ | 1 | Harshit | | 2 | Rahul | | 3 | Aarav | +----+---------+ 3 rows in set (0.00 sec)Now, we have the ...
Read MoreHow can we upload data into multiple MySQL tables by using mysqlimport?
With the help of mysqlimport we can upload data into multiple MySQL tables. It is illustrated in the example below −ExampleSuppose we want to upload the following data from two data files namely student1_tbl.txt −1 Saurav 11th 2 Sahil 11th 3 Digvijay 11thAnd House.txt1 Furniture 2 Television 3 RefrigeratorFollowings are MySQL tables into which we want to upload the above data −mysql> DESCRIBE Student1_tbl; +--------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------+-------------+------+-----+---------+-------+ | RollNo | int(11) ...
Read MoreOn passing an out-of-range value in UNIX_TIMESTAMP() or FROM_UNIXTIME() function, what MySQL will return?
When we pass an out-of-range value in UNIX_TIMESTAMP, MySQL returns 0. The valid range of value is same as for the TIMESTAMP data type.Examplemysql> Select UNIX_TIMESTAMP('1969-01-01 04:05:45'); +---------------------------------------+ | UNIX_TIMESTAMP('1969-01-01 04:05:45') | +---------------------------------------+ | 0 | +---------------------------------------+ 1 row in set (0.00 sec)When we pass an out-of-range value in FROM_UNIXTIME, MySQL returns NULL. The valid range of values is same as for the INTEGER data type.Examplemysql> Select FROM_UNIXTIME(2147483648); +---------------------------+ | FROM_UNIXTIME(2147483648) | +---------------------------+ | NULL | +---------------------------+ 1 row in set (0.00 sec)
Read MoreHow can we insert current date and time automatically on inserting values in other columns in MySQL?
In MySQL, we can insert the current date and time automatically to a column on inserting the values in another column by declaring that column as DEFAULT CURRENT_TIMESTAMP.Examplemysql> Create table testing -> ( -> StudentName varchar(20) NOT NULL, -> RegDate TIMESTAMP DEFAULT CURRENT_TIMESTAMP -> ); Query OK, 0 rows affected (0.49 sec)Above query will create a table ‘testing’ with a column named StudentName and other column named ‘RegDate’ declared as DEFAULT CURRENT_TIMESTAMP. Now, on inserting the values i.e. names in StudentName column, the current date and time will be inserted in the other column automatically.mysql> Insert ...
Read MoreWhat are all the ways an object can be created in Java?
You can create an objectUsing new keyword.Sample obj = new Sample();Using the newInstance() method and Class.forName() method.Sample obj2 = (Sample) Class.forName("Sample").newInstance();Using the clone() method by implementing Cloneable Interface (marker).Sample obj3 = (Sample) obj1.clone();Using class loader.Object obj4 = Sample.class.getClassLoader().loadClass("Sample");Using the constructor class from lang.reflect.Class cls = Sample.class; Constructor obj = cls.getDeclaredConstructors()[0]; Sample obj5 = (Sample) obj.newInstance();
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