JDBC is a layer of abstraction that allows users to choose between databases. It allows

you to change to a different database engine and to write to a single API. JDBC allows you

to write database applications in Java without having to concern yourself with the

underlying details of a particular database.

What is JDBC Driver interface?

The JDBC Driver interface provides vendor-specific implementations of the abstract classes

provided by the JDBC API. Each vendors driver must provide implementations of the

java.sql.Connection,Statement,PreparedStatement, CallableStatement, ResultSet and Driver.

What are the common tasks of JDBC?

Create an instance of a JDBC driver or load JDBC drivers through jdbc.drivers

Register a driver

Specify a database

Open a database connection

Submit a query

Receive results

What are the  commonly  used Classes & Interfaces in JDBC?

There are 8 classes: java.sql.Driver, Connection,Statement, PreparedStatement,DriverManager

CallableStatement, ResultSet, ResultSetMetaData, DatabaseMetaData.

What are the flow statements of JDBC?

A URL string

-->getConnection-->DriverManager-->Driver-->Connection-->Statement-->executeQuery-->ResultSet.

What are the steps involved in establishing a connection?

This involves two steps: (1) loading the driver and (2) making the connection.

How can you load the drivers?

Loading the driver or drivers you want to use is very simple and involves just one line of

code. If, for example, you want to use the JDBC-ODBC Bridge driver, the following code

will load it:

Eg.

Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");

Your driver documentation will give you the class name to use. For instance, if the class

name is jdbc.DriverXYZ , you would load the driver with the following line of code:

E.g.

Class.forName("jdbc.DriverXYZ");

What Class.forName will do while loading drivers?

It is used to create an instance of a driver and register it with the DriverManager. When

you have loaded a driver, it is available for making a connection with a DBMS.

How can you make the connection?

In establishing a connection is to have the appropriate driver connect to the DBMS. The

following line of code illustrates the general idea:

E.g.

String url = "jdbc:odbc:red";

Connection con = DriverManager.getConnection(url, "Admin", "tiger");

How can you create JDBC statements?

A Statement object is what sends your SQL statement to the DBMS. You simply create a

Statement object and then execute it, supplying the appropriate execute method with the

SQL statement you want to send. For a SELECT statement, the method to use is executeQuery.

For statements that create or modify tables, the method to use is executeUpdate. E.g. It

takes an instance of an active connection to create a Statement object. In the following

example, we use our Connection object con to create the Statement object stmt :

Statement stmt = con.createStatement();

How can you retrieve data from the ResultSet?

First JDBC returns results in a ResultSet object, so we need to declare an instance of the

class ResultSet to hold our results. The following code demonstrates declaring the

ResultSet object rs.

E.g.

ResultSet rs = stmt.executeQuery("SELECT NAME, SAL FROM Employee");

Second:

String s = rs.getString("NAME");

The method getString is invoked on the ResultSet object rs , so getString will retrieve

(get) the value stored in the column NAME in the current row of rs

What are the different types of Statements?

1.Statement (use createStatement method) 2. Prepared Statement (Use prepareStatement

method) and 3. Callable Statement (Use prepareCall)

How can you use PreparedStatement?

This special type of statement is derived from the more general class, Statement. If you

want to execute a Statement object many times, it will normally reduce execution time to

use a PreparedStatement object instead. The advantage to this is that in most cases, this

SQL statement will be sent to the DBMS right away, where it will be compiled. As a result,

the PreparedStatement object contains not just an SQL statement, but an SQL statement that

has been precompiled. This means that when the PreparedStatement is executed, the DBMS can

just run the PreparedStatement 's SQL statement without having to compile it first.

E.g.

PreparedStatement updateSales = con.prepareStatement("UPDATE Employee SET SAL= ? WHERE DEST LIKE ?");

How to call a Stored Procedure from JDBC?

The first step is to create a CallableStatement object. As with Statement an and

PreparedStatement objects, this is done with an open Connection object. A

CallableStatement object contains a call to a stored procedure;

E.g.

CallableStatement cs = con.prepareCall("{call SHOW_EMPLOYEES}");

ResultSet rs = cs.executeQuery();

How to Retrieve Warnings?

SQLWarning objects are a subclass of SQLException that deal with database access warnings.

Warnings do not stop the execution of an application, as exceptions do; they simply alert

the user that something did not happen as planned. A warning can be reported on a

Connection object, a Statement object (including PreparedStatement and CallableStatement

objects), or a ResultSet object. Each of these classes has a getWarnings method, which you

must invoke in order to see the first warning reported on the calling object

E.g.

SQLWarning warning = stmt.getWarnings();

if (warning != null) {

while (warning != null) {

System.out.println("Message: " + warning.getMessage());

System.out.println("SQLState: " + warning.getSQLState());

System.out.print("Vendor error code: ");

System.out.println(warning.getErrorCode());

warning = warning.getNextWarning();

}

}

How to Make Updates to Updatable Result Sets?

Another new feature in the JDBC 2.0 API is the ability to update rows in a result set

using methods in the Java programming language rather than having to send an SQL command.

But before you can take advantage of this capability, you need to create a ResultSet

object that is updatable. In order to do this, you supply the ResultSet constant

CONCUR_UPDATABLE to the createStatement method.

E.g.

Connection con = DriverManager.getConnection("jdbc:mySubprotocol:mySubName");

Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,

ResultSet.CONCUR_UPDATABLE);

ResultSet uprs = ("SELECT NAME, SAL FROM Employee");