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Embedded SQL
Embedded OQL (Jasmine ODQL)
Chapter 21 + 28.8 in third edition
Chapter 29.7 + Appendix E in fourth edition
Article: SQLJ: It’s Javalicious!
Chapter 8 in ”Principles of Database Systems with Internet
and Java™ Applications”
Excerpt from ”Database Systems the complete book”
Jasmine On-line Documentation
ODMG 3.0 / ODMG 2.0
(Chapter 26 in third edition / Chapter 27 in fourth edition )
nikos dimitrakas
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What is embedded SQL?
• Host Language
– Any programming language
• Database
– An SQL database (relational database)
• Embedded SQL:
– Helps the host language communicate with the
database via SQL
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Why embedded SQL?
• Advanced logic
• Database Interface/Application
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Static vs. Dynamic
• Static embedded SQL
– Compiled in advance  Faster at run-time
– Limited functionality
• Dynamic embedded SQL
– Not compiled in advance  Slower
– Full functionality
Everything that can be achieved with static embedded
SQL, can also be achieved with dynamic embedded SQL
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Standard embedded SQL vs.
embedded SQL for Java
• Standard embedded SQL
– Static
– Dynamic
• Embedded SQL for Java
– Static (i.e. SQLj)
– Dynamic (i.e. JDBC)
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Standard embedded SQL
• Defined for a number of ”older” languages:
–
–
–
–
–
–
ADA
C
COBOL
FORTRAN
PASCAL
PL/1
• ISO standard
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Standard embedded SQL
Basics
All SQL-commands start with
EXEC SQL
And are terminated with the appropriate
command-terminator (t ex ;) based on the
host language
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Standard embedded SQL
Example (singleton select)
…
EXEC SQL CONNECT myDB;
EXEC SQL SELECT name, address
INTO :lname, :laddress
FROM myTable
WHERE id=53;
…
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Standard embedded SQL
Example
Begin
EXEC SQL DECLARE mycursor CURSOR FOR
SELECT name, pet
FROM Person, Pet
WHERE Person.name = Pet.name;
. . .
EXEC SQL OPEN mycursor;
. . .
EXEC SQL FETCH mycursor INTO :lname, :lpet;
While SQLCODE = 0 Do
Begin
Writeln(lname, lpet);
EXEC SQL FETCH mycursor INTO :lname, :lpet;
End;
. . .
EXEC SQL CLOSE mycursor;
End.
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Standard embedded SQL
Exempel
VAR query : CHAR(1000);
. . .
query := ’DELETE FROM Employee WHERE enumber =
’0025’;
EXEC SQL PREPARE statement FROM :query;
EXEC SQL EXECUTE statement;
query := ’DELETE FROM Employee WHERE enumber =
’0026’;
EXEC SQL EXECUTE IMMEDIATE :query;
tablename := ’myTable’;
query := ’DELETE FROM :tablename;
EXEC SQL EXECUTE IMMEDIATE :query;
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Java embedded SQL
General
•
•
•
•
Java program
JDBC driver
(JDBC-ODBC bridge + ODBC driver)
Database
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Java embedded SQL
Arcitecture
Java Application
JDBC driver manager
JDBC/ODBC
bridge
JDBC Driver
(DBMS Specific)
ODBC Driver
DBMS
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JDBC sequence
1. Import Packages
2. Register JDBC Driver
3. Open a Connection to the database
4. Create a Statement
5. Execute an SQL command and receive a Result Set
(if there is one)
6. Process/Work with the Result Set
(back to point 4)
7. Close the Result Set and the Statement
8. Close the Connection
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1. Import Packages
//Import packages
import java.sql.*; //JDBC packages
//other packages
import java.util.*;
…
java.sql package specification:
http://java.sun.com/j2se/1.5/docs/api/index.html
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2. Register JDBC Driver
//Load IBM DB2 driver
Class.forName (”com.ibm.db2.jcc.DB2Driver”);
//Load JDBC-ODBC driver bridge
Class.forName(”sun.jdbc.odbc.JdbcOdbcDriver”);
// Load Oracle driver
DriverManager.registerDriver (new
oracle.jdbc.driver.OracleDriver());
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3. Open a Connection to the
database
String
String
String
String
String
userID = ”dbuser”;
password = ”abc123”;
ODBCURL = ”jdbc:odbc:mydb”;
ORACLEURL = ”jdbc:oracle:mydb”;
DB2URL = ”jdbc:db2:mydb”;
Connection con1 = DriverManager.getConnection (ORACLEURL,
userID, password);
Connection con2 = DriverManager.getConnection (ODBCURL,
userID, password);
Connection con3 = DriverManager.getConnection
(DB2URL, userID, password);
con3.setAutoCommit(true);
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3. Open a Connection to the
database, cont.
The URL (”database address”) is compised of three parts:
jdbc:databasetype/ODBC:databasename/ODBC-alias
ODBC-aliases can be defined in
the ODBC Manager (”Data
Sources (ODBC)” in the
Administrative Tools in the
Control Panel or by running
odbcad32.exe found in system32):
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4. Create a Statement
PreparedStatement pstmt1 =
con1.prepareStatement ("SELECT hotelname,
rating FROM hotel WHERE city = ?");
pstmt1.setString(1, ”Hawai”);
PreparedStatement pstmt2 =
con1.prepareStatement (”UPDATE event SET
place = ? Price = ? WHERE activity = ?");
pstmt2.setString(1, ”beach”);
pstmt2.setInt(2, 100);
pstmt2.setString(3, ”swimming”);
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5. Execute an SQL command and
receive a Result Set (if there is one)
//execute the prepared statement pstmt1 and
store the result in a result set
ResultSet rs = pstmt1.executeQuery();
//execute the prepared statement pstmt2
pstmt2.executeUpdate();
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6. Process/Work with the Result Set
// Print a list of the hotels that were
returned by the query
System.out.println(”Hotels in Hawai:”);
while (rs.next())
{
System.out.println (rs.getString(”hotelname”));
}
//Alternatively
rs.getString(1)
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7. Close the Result Set the Statement
8. Close the Connection
// close the result set, statements,
and the connections
rs.close();
pstmt1.close();
pstmt2.close();
con1.close();
con2.close();
con3.close();
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Data types
It is often necessary to map the database data types
to the Java data types/classes:
• SQL integer can be mapped to Java int
• SQL number, real etc can be mapped to Java real
• SQL varchar, char, string etc can be mapped to Java
String
• SQL date, time, timestamp etc can be mapped to
Java java.sql.Date, java.sql.Time,
java.sql.Timestamp
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SQLJ
SQLJ uses and extends the JDBC infrastructure.
It uses contexts in order to distinguish connections
All SQLJ database commands start with #sql
It creates profiles that contain information about the SQL
commands (so that they can be handled as static
commands)
SQLJ Java packages: sqlj.runtime
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SQLJ architecture
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SQLJ sequence
1. Import Packages
2. (Define iterator)
3. Register JDBC Driver
4. Open a Connection to the database
5. Set DefaultContext / other Context
6. Execute an SQL command and receive the result (if there is
any)
7. Process/Work with the result (cursor)
(back to point 6)
8. Close the cursor
9. Close the Connection/Context
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1. Import Packages
//Import packages
import sqlj.runtime.*;
import sqlj.runtime.ref.*;
import java.sql.*; //JDBC packages
import java.util.*;
sqlj package specification:
ftp://ftp.calweb.com/business/sqlj/SQLJ-P0.pdf
http://www.ifis.mu-luebeck.de/lehre/ss99/prakt/informixjdbc-doc/sqlj/doc/runtime/javadoc/packages.html
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2. (Define iterator)
#sql iterator Hotel_Cursor (String
hotelname, Integer rooms) ;
#sql iterator String2_Cursor (String,
String);
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3. Register JDBC Driver
//Load IBM DB2 driver
Class.forName (”com.ibm.db2.jcc.DB2Driver”);
//Load JDBC-ODBC driver bridge
Class.forName(”sun.jdbc.odbc.JdbcOdbcDriver”);
// Load Oracle driver
DriverManager.registerDriver (new
oracle.jdbc.driver.OracleDriver());
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4. Open a Connection to the
database
String
String
String
String
String
userID = ”dbuser”;
password = ”abc123”;
ODBCURL = ”jdbc:odbc:mydb”;
ORACLEURL = ” jdbc:oracle:mydb”;
DB2URL = ”jdbc:db2:mydb”;
Connection con1 = DriverManager.getConnection (ORACLEURL,
userID, password);
Connection con2 = DriverManager.getConnection (ODBCURL,
userID, password);
Connection con3 = DriverManager.getConnection
(DB2URL, userID, password);
con3.setAutoCommit(true);
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5. Set DefaultContext / other
Context
// Set the default context so SQLJ can automatically
pick up the connection
DefaultContext ctx = new DefaultContext (con3);
DefaultContext.setDefaultContext (ctx);
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6. Execute an SQL command and
receive the result (if there is any)
int rooms = 500;
String name = ”Grand";
String city = ”Madrid”;
#sql { INSERT INTO hotel (hotelname, rooms,
city) VALUES (:name, :rooms, :city) };
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6. Execute an SQL command and
receive the result (if there is any)
String city = ”Rome”;
Hotel_Cursor hotelcursor;
#sql hotelcursor = {SELECT hotelname, rooms
FROM hotel WHERE city = :city };
String2_Cursor hotel200cursor;
#sql hotel200cursor = {SELECT hotelname, city
FROM hotel WHERE rooms >= 200 };
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7. Process/Work with the result
(cursor)
// Print a list of the hotels that were
returned by the first query
System.out.println(”Hotels in Rome:”);
while (hotelcursor.next())
{
System.out.print(hotelcursor.hotelname());
System.out.print(” ”);
System.out.println(hotelcursor.rooms());
}
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7. Process/Work with the result
(cursor)
// Print a list of the hotels that were returned by
the second query
String s1;
String s2;
System.out.println(”Hotels with 200 or more rooms:”);
while (true)
{
#sql { FETCH :hotel200cursor INTO :s1, :s2 };
if (hotel200cursor.endFetch())
break;
System.out.println (s1 + "\t” + s2);
}
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8. Close the cursor
9. Close the Connection/Context
// close the cursors and the
connection/context
hotelcursor.close();
hotel200cursor.close();
ctx.close(); //this will close the
connection con3 as well
ctx.close(false); //keep the connection
alive
con3.close(); //close only the connection
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More information
• JDBC (SUN):
http://java.sun.com/products/jdbc/index.html
• SQLJ:
http://www.sqlj.org/
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OQL, ODQL & embedded OQL, ODQL
• Hard to define a border
• Depends on the OODBMS
• compare SQL – Stored Procedure – Embedded
SQL
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Embedded OQL/ODQL
• OO programming language
– Java
– C++
– …
• OODBMS
–
–
–
–
Jasmine
Objectivity
FastObjects
…
• Classes
– Database specific classes, or
– JDO Classes and JDO enhanced database classes
• Query Language
– Database specific query language, or
– JDOQL
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Embedded OQL/ODQL Architecture
Java Application
JDO classes
JDO Enhanced
Database
Java Classes
Database
Java Classes
OODBMS-specific classes
OODBMS
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OQL (example)
select e.ssn, count(e.teaches)
from e in Instructor
where e.dept.name = "D1"
and count(e.teaches) > 0
select Instructor
from Instructor
where Instructor.dept.name = "D1”
and Instructor.teaches.count() > 0
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Embedded OQL (C++)
#include …
…
%for each v in select e.ssn, count(e.teaches)
from e in Instructor
where e.dept.name = "D1"
and count(e.teaches) > 0
do %print v;
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Jasmine ODQL
defaultCF …;
…
Instructor set vs, v;
vs = select Instructor from Instructors
where Instructor.dept.name == "D1”
and Instructor.teaches.count() > 0;
scan (vs, v)
{
v.ssn.print();
v.teaches.count().print();
};
end;
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Embedded Jasmine ODQL i Java
import jp.jasmine.japi.*;
…
db = new Database();
…
ODQLStatement odql = db.getODQLStatement();
odql.defaultCF("myCF");
odql.execute("Instructor set vs;");
odql.execute("vs = select Instructor from Instructor where
Instructor.dept.name == \"D1\" and
Instructor.teaches.count() > 0;");
DBCollection instructors = (DBCollection) odql.getVar(“vs");
Enumeration instructorsEnum = instructors.elements();
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Embedded Jasmine ODQL i Java
odql.execute("Instructor v;");
while (instructorsEnum.hasMoreElements())
{
DBObject v = (DBObject)
instructorsEnum.nextElement();
String ssn = (String) v.getProperty(“ssn");
System.out.println(ssn);
odql.defineVar("amount", new Integer(0));
odql.setVar("v", v);
odql.execute("amount = v.teaches.count();");
System.out.println(odql.getIntVar("amount"));
}
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Jasmine ODQL
ODQL (Object Definition and Query
Language) is an integrated object language
that provides facilities for object definition,
object manipulation and object query.
ODQL statements can either be embedded
and compiled in a host language, or
interpreted using the supplied ODQL
interpreter
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Jasmine ODQL (structure)
defaultCF database name
Variable declaration
Program code
All commands must be terminated with
;
end;
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Jasmine ODQL
if (condition)
{program code};
else
{program code};
(common constructs)
while (condition)
{program code};
scan (set, element variable)
{program code};
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Jasmine ODQL
(useful methods)
Set methods:
User defined methods:
unique()
hasElement(element)
hasSameElements(set)
union(set)
count()
…
Can be defined for a class!
nikos dimitrakas
For example:
age() can be a method
defined for the class
Person and it calculates
the person’s age based
on the date of birth.
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Jasmine ODQL
(example)
defaultCF myCF;
Person set ps, p;
Job set js, j;
Integer totalsalary;
/*All people that live in Stockholm and are over 18*/
ps = select Person from Person where Person.age() > 18
and Person.homeaddress.city == "Stockholm";
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Jasmine ODQL
(example cont.)
scan (ps, p)
{
totalsalary = 0;
p.name.print();
p.isRich().print();
p.jobs.count().print();
js = p.jobs;
scan (js, j)
{
totalsalary = totalsalary + j.salary;
j.description.print();
j.salary.print();
};
totalsalary.print();
};
end;
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Jasmine Java support classes (J-API)
• Database
– Manages database sessions and transactions.
• DBObject
– Supports instance-level operations, such as manipulating properties
and invoking methods.
• DBClass
– Supports class-level operations, such as manipulating properties and
invoking methods.
• DBCollection
– Supports Jasmine collections.
• ODQLStatement
– Supports executing ODQL statements and manipulating ODQL
variables.
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Jasmine J-API sequence
1. Import Packages
2. Open a Connection to the database
2a. Start a session and a transaction
3. Get an ODQL Statement object
3a. Set the default Class Family
4. Execute ODQL statements or other commands
through the ODQL statement object
5. Work with data in Java
(back to 4)
6. End the transaction, session and connection
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1. Import Packages
import jp.jasmine.japi.*;
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2. Open a Connection to the database
2a. Start a session and a transaction
db = new Database();
db.startSession();
db.startTransaction();
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3. Get an ODQL Statement object
3a. Set the default Class Family
ODQLStatement odql =
db.getODQLStatement();
odql.defaultCF("CAStore");
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4. Execute ODQL statements or other
commands through the ODQL statement object
5. Work with data in Java
odql.execute("Customer set vs;");
odql.execute("vs = select Customer from Customer
where Customer.orders.count() > 2;");
DBCollection customers = (DBCollection)
odql.getVar("vs");
Enumeration customersEnum =
customers.elements();
while (customersEnum.hasMoreElements())
{
DBObject v = (DBObject)
customersEnum.nextElement();
String name = (String) v.getProperty("name");
System.out.println(name);
}
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6. End the transaction, session and connection
db.endTransaction();
db.endSession();
db.close();
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More information
• OODBMS documentation
– Jasmine: Jasmine On-Line Documentation
• Jasmine J-API
– Programmer’s Guide for Java Proxies (Jp)
C:\Jasmine\Doc\ODB\jp.pdf
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