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If all the values in MySQL COALESCE() function are NULL then it returns NULL as the output. It means that this function does not find any non-NULL value in the list.Examplemysql> Select COALESCE(NULL, NULL, NULL, NULL); +----------------------------------+ | COALESCE(NULL, NULL, NULL, NULL) | +----------------------------------+ | NULL | +----------------------------------+ 1 row in set (0.00 sec)
The syntax of SUBSTRING() function using FROM and FOR keywords is the standard MySQL syntax.SyntaxSUBSTRING(str FROM pos FOR len)Here, str is the string from which substring would be returned.Pos is the starting position of substring.Len is the length of substring i.e. the total number of characters fetched from str.Examplemysql> Select SUBSTRING('foobarbar' FROM 4 FOR 5); +-------------------------------------+ | SUBSTRING('foobarbar' FROM 4 FOR 5) | +-------------------------------------+ | barba | +-------------------------------------+ 1 row in set (0.00 sec)The result set above, makes the use of FROM and FOR keywords very much clear in SUBSTRING() function.
To make it understand, we are using the following data from a table named ‘customerdetail’.mysql> Select * from Customerdetail; +----------------------+----------------------+-----------+---------------------+ | Name | FName | Address | Emailid | +----------------------+----------------------+-----------+---------------------+ | Advik Jhamb | Lovkesh Jhamb | Mumbai | Advik@gmail.com | | Chirag Jai Patil | Raman Jai Patil | Gujrat | chirahp@yahoo.com | | Devansh Singh Rajput | Kishore Singh Rajput ... Read More
MySQL SUBSTRING_INDEX() function can accept the negative value of argument ‘count’ and in this case, it returns the substring from the right of the final delimiter.Examplemysql> Select SUBSTRING_INDEX('www.google.com','.',-2); +------------------------------------------+ | SUBSTRING_INDEX('www.google.com','.',-2) | +------------------------------------------+ | google.com | +------------------------------------------+ 1 row in set (0.00 sec) mysql> Select SUBSTRING_INDEX('www.google.com','.',-1); +------------------------------------------+ | SUBSTRING_INDEX('www.google.com','.',-1) | +------------------------------------------+ | com | +------------------------------------------+ 1 row in set (0.00 sec)
Suppose we have a table named ‘ipaddress’ which contains the IP addresses as its values in column ‘IP’ as follows −mysql> Select * from ipaddress; +-----------------+ | ip | +-----------------+ | 192.128.0.5 | | 255.255.255.255 | | 192.0.255.255 | | 192.0.1.5 | +-----------------+ 4 rows in set (0.10 sec)Now with the help of SUBSTRING_INDEX() function in the following query, we can divide the IP address in four octets −mysql> Select IP, SUBSTRING_INDEX(ip, '.', 1)AS '1st Part', -> SUBSTRING_INDEX(SUBSTRING_INDEX(ip, '.', 2), '.', -1)AS '2nd Part', ... Read More
A JList is a component that can extend JComponent class used to display a list of objects that allows the user to select one or more items.There are three types of selection modes for a JList in JavaListSelectionModel.SINGLE_SELECTION: Only one list index can be selected at a time.ListSelectionModel.SINGLE_INTERVAL_SELECTION: Only one contiguous interval can be selected at a time.ListSelectionModel.MULTIPLE_INTERVAL_SELECTION: In this mode, there is no restriction on what can be selected. This is a default mode.Exampleimport java.awt.*; import java.awt.event.*; import javax.swing.*; public class JListSelectionModeTest extends JFrame implements ActionListener { private JList list; private DefaultListModel listModel; public JListSelectionModeTest() { ... Read More
With the help of ‘mysqladmin’ along with ‘status’ option program we would be able to check the status of MySQL server. It can be used as follows on command line −C:\mysql\bin>mysqladmin -u root status Uptime: 3865 Threads: 1 Questions: 50 Slow queries: 0 Opens: 113 Flush tables: 1 Open tables: 102 Queries per second avg: 0.012
We need to use ‘mysqlcheck’ client program along with –analyze option to analyze the tables of a particular database. Its syntax would be as follows −Mysqlcheck – u root –analyze db_nameExampleThe following command will analyze the tables of database ‘query’ −C:\mysql\bin>mysqlcheck -u root --analyze query query.cars OK query.copy_cars OK query.countries Table is already up to date query.customers ... Read More
We need to use ‘mysqlshow’ client program along with the name of the database to get the list of tables in a particular database. Its syntax would be as follows −Mysqlshow – u root db_name [pat_matching]Here db_name would be the name of the database from which we want to get the name of tables.Pat_matching is optional. It is used to get the list of the tables of some specific pattern. If we will not provide any pattern then it will show all the tables stored in that database.ExampleThe following command will get all the tables of database ‘query’ −C:\mysql\bin>mysqlshow -u ... Read More
JPanelA JPanel is a subclass of JComponent (a subclass of a Container class). Therefore, JPanel is also a Container.A JPanel is an empty area that can be used either to layout other components including other panels.In a JPanel, we can add fields, labels, buttons, checkboxes, and images also.The Layout Managers such as FlowLayout, GridLayout, BorderLayout and other layout managers helps us to control the sizes, positions, and alignment of the components using JPanel.The important methods of a JPanel class are getAccessibleContext(), getUI(), updateUI() and paramString().We can also implement a JPanel with vertical and horizontal scrolls by adding the panel object to JScrollPane.Exampleimport java.awt.*; ... Read More