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Articles by Nancy Den
Page 16 of 18
What is the difference between execute(), executeQuery() and executeUpdate() methods in JDBC?
Once you have created the statement object you can execute it using one of the execute methods of the Statement interface namely, execute(), executeUpdate() and, executeQuery().The execute() method: This method is used to execute SQL DDL statements, it returns a boolean value specifying weather the ResultSet object can be retrieved.Exampleimport java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.sql.Statement; public class Example { public static void main(String args[]) throws SQLException { //Registering the Driver DriverManager.registerDriver(new com.mysql.jdbc.Driver()); //Getting the connection String mysqlUrl = "jdbc:mysql://localhost/sampleDB"; Connection con = ...
Read MoreCan we create a table with a space in name in MySQL?
To create a table with a space in the table name in MySQL, you must use backticks otherwise you will get an error.Let us first see what error will arise by creating a table with a space in the name i.e. “Demo Table” table name below:mysql> create table Demo Table ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, EmployeeFirstName varchar(20), EmployeeLastName varchar(20), EmployeeAge int, EmployeeSalary int, EmployeeAddress varchar(200) ); ERROR 1064 (42000): You have an error in your syntax; check the manual that corresponds to your MySQL server version for the right syntax to ...
Read MoreI/O-mapped I/O or memory-mapped I/O in 8085 Microprocessor
Before having a discussion regarding the demerits or merits of I/O mapped I/O and memory-mapped I/O, let us have a generic discussion regarding the difference between I/O mapped I/O and memory mapped I/O.In Memory Mapped Input Output −We allocate a memory address to an Input-Output device.Any instructions related to memory can be accessed by this Input-Output device.The Input-Output device data are also given to the Arithmetic Logical Unit.Input-Output Mapped Input Output −We give an Input-Output address to an Input-Output deviceOnly IN and OUT instructions are accessed by such devices.The ALU operations are not directly applicable to such Input-Output data.So as ...
Read MoreControl port of 8255
In 8255, there are two types of command words or control word are available. And they are −Mode definition control word andPort C bit set/reset control word.Both these are written to the control port only. From the point of view of the microprocessor there is a single 8-bit control port, which is selected when CS* = 0, WR* = 0, A1 = 1 and A0 = 1. But if we consider the architecture of 8255, internally there are two control ports, one for mode definition control and another for Port C bit set/reset control. The contents of the control port ...
Read MoreWhat is ResultSetMetaData in JDBC? What is its significance?
The ResultSetMetaData provides information about the obtained ResultSet object like, the number of columns, names of the columns, datatypes of the columns, name of the table etc…Following are some methods of ResultSetMetaData class.MethodDescriptiongetColumnCount()Retrieves the number of columns in the current ResultSet object.getColumnLabel()Retrieves the suggested name of the column for use.getColumnName()Retrieves the name of the column.getTableName()Retrieves the name of the table.Exampleimport java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.Statement; public class ResultSetMetadataExample { public static void main(String args[]) throws Exception { //Registering the Driver DriverManager.registerDriver(new com.mysql.jdbc.Driver()); //Getting the connection ...
Read MoreHow many locking systems are there in JDBC?
You can lock a record, set of records, database table, table-space etc. and when we do we cannot change the locked values. Following are the types of locking in JDBC:Row and Key Locks: These are used to lock a particular row. Using these locks, you can achieve concurrency.Page Locks: These are used to lock a page. If you apply this, whenever the contents of a row changes, the database locks the entire page which holds the row. If you need to update/change large number of rows at once you can use this lock.Table Locks: You can lock a table using ...
Read MoreWhat is the use of the method setAutoCommit() in JDBC?
If you commit a database, it saves all the changes that have been done till that particular point.You can commit a database using the commit() method. Whenever any issue occurs you can revert the database to this point using the rollback() method. By default, some databases commit the databases automatically. But, while managing transactions you need to commit the database manually.In this scenario you can use the setAutoCommit() method. This method belongs to the Connection interface and, it accepts a boolean value.If you pass true to this method it turns on the auto-commit feature of the database and, if you ...
Read MoreHow many types of Result Sets are there in JDBC What are they?
There are two types of result sets namely, forward only and, bidirectional.Forward only ResultSet: The ResultSet object whose cursor moves only in one direction is known as forward only ResultSet. By default, JDBC result sets are forward-only result sets.You can move the cursor of the forward only ResultSets using the next() method of the ResultSet interface. It moves the pointer to the next row from the current position. This method returns a boolean value. If there are no rows next to its current position it returns false, else it returns true.Therefore, using this method in the while loop you can ...
Read MoreWhat are the important methods of the SQLException class?
An SQLException can occur both in the driver and the database. When such an exception occurs, an object of type SQLException will be passed to the catch clause.The passed SQLException object has the following methods available for retrieving additional information about the exception:MethodDescriptiongetErrorCode( )Gets the error number associated with the exception.getMessage( )Gets the JDBC driver's error message for an error, handled by the driver or gets the Oracle error number and message for a database error.getSQLState( )Gets the XOPEN SQLstate string. For a JDBC driver error, no useful information is returned from this method. For a database error, the five-digit ...
Read MoreWhat is JDBC SQL Escape Syntax Explain?
The escape syntax gives you the flexibility to use database specific features unavailable to you by using standard JDBC methods and properties.The general SQL escape syntax format is as follow:{keyword 'parameters'}Following are various escape syntaxes in JDBC:d, t, ts Keywords: They help identify date, time, and timestamp literals. As you know, no two DBMSs represent time and date the same way. This escape syntax tells the driver to render the date or time in the target database's format{d 'yyyy-mm-dd'}Where yyyy = year, mm = month; dd = date. Using this syntax {d '2009-09-03'} is March 9, 2009.Example//Create a Statement object ...
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