JDBC Final

7/31/2019 JDBC Final

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PreparedStatement

CallableStatement

ResultSetDatabase MetaData


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Packagejava.sql.PreparedStatement

PreparedStatement(PS) Object is used toexecute the parametrized SQL statement.

PS object supports zero or more INparameters.

PS object represents a precompiled query that

can be executed multiple times withoutcompiling again and again.


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PS object represent a pre-compiled SQLstatement, so that the execution of the SQLstatement is much faster as compared to theStatement object.

java.sql.PreparedStatement is a subtype of thejava.sql.Statement interface, therefore it inheritsall the properties of the Statement interface.


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Important Points about PS are as follows:

A PreparedStatement object is associated with aConnection object.

A PS object represent the execution plan of anSQL statement saved into the database that is

passed as a parameter while creating the PSobject.

SQL statement can take parameters whosevalues can be set while operation.

A PS is implicitly closed after the Connectionobject on which the PS object was created isclosed.


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ConnectionObject

con

Java Application JDBC Driver

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3) Compile the givenSQL Statement

4) Prepare anexecution plan toexecute the SQLstatement

5) Store the executionplan with unique ID

12) Locate theexecution plan

13) Execute the planwith the given data

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ps

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PreparedStatement Object

setXXX()

executeXXX()

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result

Steps involved in Using Prepared Statement


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set methods of PreparedStatement

ReturnType

Methods

void setArray(int parameterIndex,Arrayx)

Sets the designated parameter to the given java.sql.Array object.

void setBinaryStream(int parameterIndex, InputStream x)Sets the designated parameter to the given input stream.

void setBinaryStream(int parameterIndex, InputStream x, int length)Sets the designated parameter to the given input stream, which will have

the specified number of bytes.void setBoolean(int parameterIndex, boolean x)

Sets the designated parameter to the given Java boolean value.

void setDate(int parameterIndex, Date x)

void setDouble(int parameterIndex, double x)

void setFloat(int parameterIndex, float x)

void setInt(int parameterIndex, int x)

void setLong(int parameterIndex, long x)

void setObject(int parameterIndex, Object x)

void setString(int parameterIndex, String x)


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It improves the performance of application, wheresame query is to be executed no. of times.

It is easier to insert or update the SQL 99 datatype columns, such as BLOB, CLOB, or OBJECT

It provides a programmatic approach to set thevalues of parameters in a more descriptive way.


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It can represent only one SQL statement.Therefore, we cannot execute more than onestatement by a single PreparedStatement.

It supports to add only a single SQL statement tobe executed for multiple times with different set ofvalues it a batch.


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Broad level steps to use PreparedStatement:1. Create a PreparedStatement object

2. Set the values for the Parameters3. Execute the PreparedStatement

Creating a PreparedStatement object

Created by using the prepareStatement(StringsqlStatement) method of the Connection object.

Connection object submits the SQL statement, anddatabase returns an identity of the execution plan

prepared for the SQL statement, if compilation wassuccessful.

prepareStatement(String) method can contain a zeroor more question marks(?, known as prameters


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Values can be set for? after the SQL statement is

compiled, i.e. after creating PS object or beforeexecuting the statement.

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

Connection con =DriverManager.getConnection(url,user,password);

String sqlSt = insert into mytable values(?,?,?);

PreparedStatement ps = con.prepareStatement(sqlSt);

//ps refers to the PS object created by using theConnection object.


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The PS object supports setter methods for allthe data types supported by Java.

It accepts two argument. First, indicateparameter index. Second, indicates value for

parameter.Eg:-

ps.setString(1,abc1);ps.setInt(2,38);ps.setDouble(3,158.75);

Note :- The parameter index starts from 1, fromleft to right of the statement.


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After preparing and initializing the PS object, wecan execute the SQL statement with theconfigured parameter.

execute() returns boolean,

executeUpdate() return int,executeQuery() returns ResultSet

methods of the PS object are used to execute theSQL statement.

int n = ps.executeUpdate();

//n holds the no. of rows or tables that re beingupdate.


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Callable statement


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In java callable statement is used to call thestored procedures and functions.

That is the procedure can be called by using anobject of the callablestatement interface.

They are use ti access,invoke, and retrive the

results of sql stored procedures,functions andcursors.


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Procedures


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Ussing callablestatement


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Calling Functions By UsingCallableStatement Most of the databases provide support for

various types of built in functions.

Some of these are:

Numeric

Strings

Time These functions are accessed by calling metadata

methods


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Function Types And Their UsesFunction

Types Uses

NumericFunctions

Stringfunctions

Time & Datefunctions

Systemfunctions

Conversion

functions

Operates on numeric data types such as greatest(),least(), length(),lower(),etc

Operates on string data types such as char(), concat(),insert(), length(),etc.

Access all the time and date related information fromdatabase.

Retrieves the information about database managementsystem

Convert data type of a given value into the required type


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Contd.

In addition to these pre-definedfunctions,DBMS provides the feature tocreate user-defined functions that can be usedin DML queries.

The user-defined functions can be used infollowing situations:

In the column names of SELECT statement.

As a condition in the WHERE clause. In the value clause of an INSERT statement.

In the SET clause of an UPDATE statement.


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Contd The following is a syntax of how to create a user-

defined function:

Create [or replace] FUNCTION function-name[(parameter[, parameter])]RETURN return_datatypeIS/AS

[Declaration_section]BEGINexecutable_section[Exception exception_section]

END [function_name];


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Contd.

The procedure to call a function in an application is

same as it is in case of stored procedures.

The syntax to invoke a function in JDBC is:

{call ?:=function_name(?,?,..)} // with string parameters

{call ?:=function_name} // with no parameter


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Using cursors in CallableStatement

A cursor defines the runtime executionenvironment for a query where the result of the

query execution can be captured.

The syntax used to create a cursor is as follows:

CREATE OR REPLACE PACKAGE package_name AS

TYPE type_name IS REF CURSOR;

END;


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Contd.

The cursor is used to retrive the ResultSetfrom a database through CallableStatement.

Following example shows the use of cursorsto get the ResultSet object to access multiple

records from a database


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Example

CREATE OR REPLACE PACKAGE mypack ASTYPE mycursor IS REF CURSOR;

END;

/

Package created CREATE OR REPLACE FUNCTION getaccountdetails(actype NUMBER )

RETURN mypack.mycursor AS

myresult mypack.mycursor;

BEGIN

OPEN myresult FORSELECT accno, name, bal FROM account WHERE acctype = acc_type;

RETURN myresult;

END;

/

Function created


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Comparing procedure and Functions

A function has areturn type.

Functions can beused with SQL DMLqueries.

A procedure issuitable to use DMLqueries .

Procedures does not have returntype,rather if needed data can bemade available through OUTparameters.

Procedures cannot be used withDML queries.

A function is not suitable to useDML queries.


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ResultSet Interface


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ResultSet Interface ResultSet is an interface packaged in the java.sql

package.

The java.sql.ResultSet interface is defined todescribe an object, known as ResultSet object.

It represents the data in tabular form that is

retrieved by executing an SQL query. ResultSet object provides access to a pseudo

table which is a result of a SQL query.

ResultSet object holds zero or more objects.


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Maintain a cursor pointing to the current row ofdata.

Initially the cursor is positioned before the firstrow.

Moved ahead by the next() method.

A default ResultSet object is not updatable andhas a cursor that moves forward only

Obtain a ResultSet Object by usingexecuteQuery() or getResultSet() method.


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public ResultSet getResultSet() throwsSQLException

Retrieves the current result as a ResultSet object. Thismethod should be called only once per result.

Returns:

the current result as a ResultSet object or null if

the result is an update count or there are no moreresults

Throws:

SQLException - if a database access error occurs


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ResultSet follows iterate pattern.

A single ResultSet object can be opened at a

time.

Obtain multiple ResultSets by using onestatement. When we try to open a ResultSet

using a statement that is already associated withan opened ResultSet, the existing ResultSet isimplicitly closed.


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StatementObject

st

Java Application JDBC Driver

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3) Compile & Executethe given SQL query

4) Cache the result intobuffer (CURSOR)

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rs

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ResultSetObject

next()boolean

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11 getXXX()

Buffer

Result TableGet row

DatafromDB buffer

ResultSet Operation


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Methods of ResultSet

absolute(int row)Moves the cursor to the given row number in this ResultSet

object.

afterLast()

Moves the cursor to the end of this ResultSet object, just afterthe last row. beforeFirst()Moves the cursor to the front of this ResultSet object, just before

the first row. close()Closes a ResultSet object and release all the JDBC resources

connected to it. deleteRow()Deletes the specified row from a ResultSet object, as well as

from the database.


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first()

Moves the cursor to the first row in a ResultSet object.

getXXX()

Retrieves the coloumn values of the specified typesfrom the current row. The type can be any of theJava predefined data types. Such as int, long, Byte,charcter, String, double etc.

insertRow()Inserts the specified row and the contents into the

ResultSet object as well as into the database.


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next()Moves the cursor down one row from its current

position. updateRow()Updates the underlying database with the new

contents of the current row of this ResultSetobject.

updateXXX()Updates the column values of the current row of

the specified types.


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Data retrieving Steps

1. Move the cursor position to the required rowInitially the cusor positioned before the first row. Use

next() method of ResultSet to move the cursor position

to the next record. It returns true if the new current rowis valid else false if there are no more rows.

2. Reading the Column ValuesAfter moving the cursor to the respective row, use the

getter methods (getXXX, getBoolean, getLong and so on)of ResultSet to retrieve the data from the row where thecursor is positioned.


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ResultSetMetaData Interface


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JDBC API provides the feature of MetaData thatcontains descriptive information about the data

available in a database. JDBC MetaData providesinformation about tables, views,columnnames,column data types, stored procedures anddatabases.

ResultSetMetaData interface offers informationabout the columns in a ResultSet, such as thecolumn name, column data type and length of thecolumn.


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Example:

ResultSet rs = stmt.executeQuery("SELECT a, b,

c FROM TABLE2");ResultSetMetaData rsmd = rs.getMetaData();

int numberOfColumns = rsmd.getColumnCount();

boolean b = rsmd.isSearchable(1);


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Methods of ResutSetMetaData getColumnCount()

Returns the number of columns in this ResultSet

object. getColumnName(int index)

Takes the column index and returns the column name

getColumnTypeName(int index)

Takes the column index and returns the databasespecific type name.

getSchemaName(int column)

Get the designated column's table's schema.


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Methods of ResutSetMetaData getTableName(int column)

Gets the designated column's table name.

getColumnClassName(int column)

Retrieves the java class name associated with theResultSet object.

isReadOnly(int column)Indicates whether the designated column is

definitely not writable.


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ResultSet Type(Package : java.sql.resultset) There Are 3 type :

1. TYPE_FORWARD_ONLYCursor movement only forward

2. TYPE_SCROLL_INSENSITIVECursor movement forward as well as backwardwithout reflecting changes

3. TYPE_SCROLL_SENSITIVECursor movement forward as well as backwardwithout reflecting changes


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Methods to Navigate ResultSetMethod Use

next() Move cursor toforwarddirection

previous() Move cursor toBackwarddirection

first() Moves cursor tofirstrow

last() Moves cursor to lastrow

relative(int rows) Moves relative to cursor positionwhere row values:0 indicate current position+ve int indicate forword move-ve int indicate backword move

Absolute(int row_number) Moves cursor to given position

beforeFirst() Moves cursor to beforefirst row

afterLst() Moves cursor to after last row

Note: 1. All methods return trueOR falseas the method affect the cursor position2. All method throws SQLExceptionexcept next()


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ResultSet Concurrency Used to determine functionality of resultSet

Two type :

1. CONCUR_READ_ONLY(Default)

2. CONCUR_UPDATABLE

To find the concurrency use :

getConcurrency()To check the supportable by driver or not use :

supportsResulrtSetConcurrency(int)where int : concurrency type


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Cursor Holdability Used to call Connection.commit()

There are 2types :

1. HOLD_CURSORS_OVER_COMMITHolds cursor when commit is called

2. CLOSE_CURSORS_AT_COMMIT

Cursor is closed when commit is called


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Manipulate data using ResultSet ObjectSteps1. Move cursor to the row where you need to

update

2. Use the ResultSet.UpdateXXX() methods tochange data (XXX-predefined data type)

3. Invoke the UpdateRow() method of ResultSetobject to reflect changes into database(to verify commitment of update use methodrowUpdated())

4. Closing connection usingResultSet.Close()


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DatabaseMetaData Interface(Package : java.sql.databasemetadata) Used to get information related to database and

driver

Used to create Generic Application To get the database details, such as vender

name, product name, version

To implement the advanced JDBC driver Syntax:

DatabaseMetaData dbmd = Connection.getMetaData()


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Methods of DatabseMetaData interface

Method Use

int getDatabaseMajorVersion() Helps in retrieve major version ofdatabase in use

int getDatabaseMinorVersion() Helps to retrieve minor version ofdatabase in use

int getDatabaseProductVersion() Helps to retrieve product name ofdatabase in use

int getDatabaseProductVersion() Helps to retrieve product version ofdatabase

int getDriverName() Helps to retrieve driver name

int getDriverVersion() Helps to retrieve driver version

int getMaxConnections() Helps to retrieve max connection to thedatabase


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JDBC Final

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