Transcript DB2 Overview

CS 433
DB2 Overview
Client Access, Queries,
Stored Procedures, JDBC
9/12/01
Jeff Derstadt & Megha Batra
Administration
Project
Proposals

Due 09/14/01 by 5PM

Email them to TAs
Please
register your group on the web
http://www.cs.cornell.edu/courses/cs433/2001fa/
Client Configuration
Must setup a client-server connection
 Server name:

 egret.csuglab.cornell.edu

Port:
 50000

Database name:
 Your
group (g7, g23, etc.)
Client Configuration

Let’s configure our client!
Command Line Queries

Connect to database
 Connect
to <database_name> user
<user_name> using <password>

Issue queries
 CREATE
TABLE <table> (<column_name>
<datatype>, …)
 INSERT INTO <table> values (…)
 SELECT <columns> from <table>
Command Line Queries

Let’s issue some queries!
Stored Procedures

Definition:
 A set
of SQL and programming language (C++/Java)
statements that are compiled into a named database
object that can be invoked by a user application

Examples:
 For
each sailor with a rating less than 5, insert her
into the “NeedsTraining” table, and email her
requesting that she sign up for additional instruction
 Converting relational tables to Xml
Stored Procedures (2)

Advantages
 Can
embed SQL in a ‘native’ programming language
 Executed on the database server: no network delay
 Compiled procedures can be invoked by any user
application
 Provides consistent functionality (don’t need to rewrite
SQL ‘inserts’, can just call a stored procedure)
Java

DB2 allows you to write stored procedures
in Java
+ Java is an easy language
- Must use some sort of bridge between the
native DB2 code and the Java Virtual Machine
to transfer data from a relational table to the
stored procedure
+/- JDBC provides this bridge: extra copy, but
easy access
DB2 to Java
Java Virtual Machine
Int sid = rs.getInt(1);
DB2
String name = rs.getString(2);
(C++)
Query
Result
1
Copy from DB2 to
JDBC storage
SID=5, NAME=Sarah
2
Result extracted
from JDBC
3
ResultSet
rs;
JDBC (Java Database Connection)
JDBC java.sql.*

Using JDBC adds additional costs
 Copy
from DB2 to JDBC ResultSet object (2)
 Copy from ResultSet object to another Java
variable (sometimes at 3)

However
 JDBC
makes issuing SQL queries and
gathering results very easy
JDBC ResultSet
Provides a simple cursor object
 A cursor is a set-of-records abstraction
that allows you to move from one row to
the next and access the columns:

rs.next()
SID
NAME
12
Sarah
13
Joe
15
Megha
rs.getString(2)
Stored Procedures

Let’s write a stored procedure that
converts a table to Xml!
Questions ??