SQL 3 and SQL Middleware

Letitia Chu

SQL Origin

Structured Query LanguageFirst developed in mid 1970s.English-like front-end query languageBased on the solid mathematical foundation of

set theory and predicate calculusDifferent versions: SQL-89, 92 and SQL3

Front-end, back-end Application

Front-end User does not need to

understand SQLGUI based, off-the-shelf,

commercial software product

Generate SQL requests, that is directed to the database

Back-endWhere things happen

behind the scenesTransparent to the

database end user Includes the actual

database server, data sources, and middleware

What is middleware?Distributed software that support interactions

between clients and serversCommon API to different vendor’s databases.Responsible to assist database client to find the

database server.Does not include

Client user interfaceServer application domainDatabase

Creating applications - integrating SQL into existing programming languages.

-Two competing approaches Embedded SQL

ESQL & SQLJ

Properties: Applications must be pre-

compiled & bound to DB. Only Support static SQL. Requires target database

to be known ahead of time.

SQL Call-Level Interface (CLI) X/Open CLI, JDBC, ODBC

& SAG CLI Properties: No precompiler required & no

need to bound to DB. Only support dynamic SQL. No need to know target

database ahead of time.

Embedded SQL (ESQL)

Defined : ISO SQL-92Syntax for embedding

SQL in C, Ada, PL/I COBOL, FORTRAN, Pascal and MUMPS

Syntax: EXEC SQL

SQL_STATEMENT;

Disadvantages:Target database must be

known when developing application.

Installation involves binding applications to each server database

Code has to recompile for each vendor’s database server

SQLJ (Java’s Embedded SQL) Put together by IBM,

Oracle and Tandem in 1997.

In 1998, SQLJ became Part 10 in ISO-SQL3.

Allows user insert SQL inside a Java program

SQLJ precompiler generates embedded JDBC calls.

Advantages

Easier than JDBCEasier compiler-time

checkingSyntax

Static SQL appears in SQLJ clauses - begins with #sql, e.g.#sql { DELETE FROM Building };

SQL Call-Level Interfaces (CLI)X/Open CLI

History In 1988, 44 vendors

created SQL Access Group (SAG) - provides a unified standard for remote database access

In 1994, SAG turned the finished CLI to X/Open, SAG CLI now known as X/Open CLI.

Functions CLI wraps SQL generated by an

application, and submit to DBMS. Supports dynamic SQL Functions correspond to the SQL-

92 specification. Provides common SQL semantics Provides common error handling

and reporting

Microsoft ODBC CLIAbout:

Open Database Connectivity Windows API standard for SQL - an extended version of SAG CLI.

Most database server vendors, e.g. IBM, Oracle and etc. – support ODBC API with their native SQL APIs.

Drawbacks: ODBC specification is controlled

by Microsoft: future is unknown.

ODBC drivers are: difficult to build and maintain have different conformance

levels, and not well documented. ODBC layers

introduce a lot of overhead (especially for updates and inserts)

are seldom as fast as native APIs.

Object CLIs: JDBC and OLE

1. JDBC Java Database Connectivity

2. OLE DB An open specification designed to build on the success of ODBC by

providing an open standard for accessing all kinds of data .

Provide CLI via object interfaces (and classes) instead of procedural APIs.

Both support distributed data access via off-the-shelf ORBs

Why is JDBC valuable?What does JDBC API do?Establish a connection with a data sourceSend queries and update statements to the data sourceProcess result.

Advantages:An application with Java VM can access

virtually any data source and run on any platform.

OLE DB and ADO

UDA (Universal Data Access)Microsoft’s new strategy where one can access

data regardless of type, format or locationOffers a common interface and middleware to

access all types of data – both SQL and non-SQL

Key components included:ADO (ActiveX Data Object), OLE DB ( Object

Linking and Embedding), and ODBC.

JDBC API vs.. ODBC and UDA

JDBC: keep simple things simple allowing more advanced

capabilities where required. ODBC cannot be use directly

in Java because it uses a C interface. Java native calls are error prone.

ODBC is hard to learn. It mixes simple and advanced

features together It has complex options even

for simple queries. Translating ODBC C API into

Java API is not desirable. Programmers no need to

worry memory management when using Java API

Before JDBC API was developed, Microsoft’s ODBC API was the most widely used, so why do we need JDBC?

Open SQL GatewaysWhat is ? Translate SQL calls into an

industry-standard common Format and Protocol (FAP).

FAP provides common wire-level protocol between client and server.

Example- IBI’s EDA/SQL ISO/SAG Remote Data

Access (RDA), IBM DRDA

Functions: Acts as the broker to

translate client API calls into FAP, transport to Server.

Provides a standard SQL interface (ESQL or CLI)

Must be able to locate server and provide catalog service.

IBI (Information Builders Incorporated) EDA (Enterprise Data Access)/ SQL

Features: It is a family of open gateway

using SQL to access over 72 relational& non-relational database servers.

Owns over 10% of the data access middleware market

Allows CORBA and Java clients to access data on the 72 databases and file structures that EDA supports today.

Supports: JDBC interface Java-based

COBRA ORB called Enterprise Component Broker (ECB)

ISO/SAG RDAAbout:One of SAG ’s original

goals - port (and extend) the RDA FAP to the TCP/IP protocol.

Functionality is equivalent to SQL-89 and SQL-92 specifications.

Why not popular? RDA is not very tolerant of

SQL deviations and extensions

Thus, it is not very popular because of its lack of vendor interest

Major vendors are not implementing it, only support by small companies.

IBM DRDA (Distributed Relational Database Architecture)

IBM is promoting DRDA as the standard for federated database interoperability.

Goal - provides interoperability for fully distributed heterogeneous relational database environments by defining the protocols (FAP) for database client-server and server-server interactions.

DRDA supporters: Major Database and gateway

companies - Oracle, Sybase, XDB, Ingres, Novell, Informix, Cincom, Micro Decisionware, Inprise (i.e. Borland), IBI, Progress, and Centura.

DRDA is the bound that ties the DB2 family together.

Drawbacks: DRDA requires all client compiles with the server’s SQL syntax and semantics, limits its level of compliance.

SQL3

What is SQL3? Latest version of SQL. Weighs over 2000 pages developed by ANSI and

ISO for the last three years.

Upward compatible with SQL-92.

major extension - addition of an extensible, object-oriented type system.

Why develop SQL3? In relational databases, tables

are usually basic types - integer, character, no extension of basic type is allowed.

OO applications, make extensive use of object features: user extensible type, complex and composite objects.

Object relational database, extends relational data model, these extensions became SQL3

SQL3 new feature: Part 2 - object extensions

SQL-92 offers no facilities to define complex data types. SQL3 Part 2 - defines the new object extension features,

allow users capture the application-specific behavior as part of the database.

Extend functions User defined functions

Extend Data types Large objects, Distinct types, Structured types

Extended Function Extended Functions: Allows user to create functions by Java or other

languages.How to create? use CREATE FUNCTION. Support function overloading.FENCED or UNFENCED; FENCED - function must run

in an address space separate from the database to protect database integrity against accidental damage that might be inflicted by the function.

Extended data types Extended data types For storage of very large

objects (images, audio, video) and manipulation of complex behavior ( components of a software design) by database application.

Structured types transform relational databases into object-relational databases, once created, can used as:

Type of column in a table Type of a table

CREATE TYPE RESIDENCE( street VARCHAR (100),

city VARCHAR (100),occupant REF(PERSON ))

CREATE TYPE DOLLAR AS NUMERIC (10, 2)

Two new build-in types: BLOB contains up to 2

gigabytes of binary data. CLOB contains up to 2

gigabytes of single-byte character data

Distinct types are the supplement of the database system’s built-in data types

SQL Part 1 to 4 Part 1: SQL / Framework

basic definition and description of SQL3

Part 2: SQL/ Foundation Covers triggers, recursive

queries, roles, collections, and object SQL

Part 3: CLI Callable Level Interface

Part 4: PSM Persistent Storage Modules

Part 4: PSM The procedure specified in SQL/PSM

cannot be invoked directly from an application, but only through SQL code.

Applied SQL invoked routine by the CALL statement

A common language to write stored procedure.

Re-evaluate error handling by defining exception handlers -allows SQL routines to respond to exception or completion conditions raised when executing stored procedures.

Part 4:PSMCREATE PROCEDURE get_info (catalog CHARACTER (10),CD_name CHARACTER VARYING (50),first_track CHARACTER VARYING (40)),

- The codes to do the work goes here…– SET CD_name = …– SET first_track = …

END PROCEDURE get_info

Calling this procedure- Directly invoked from a host

language e.g. C, COBOL is not permitted

Cdname = get_name (“MD105299 – A”); SQL invoked functions can only be invoked as part of the execution of

an SQL statementEXEC SQL SET :Cdname = get_name(“MD105299 – A”);

To invoke this procedure: CALL get_info (‘MD105299-A’, :var1, :var2);

Calling it directly from ESQLEXEC SQL CALL get_info (‘MD105299-A’, :var1, :var2);

SQL3: Part 5 to 10 Part 8:SQL Object

This is deleted since most of the extend object constructs now folded into the core SQL object model.

Part 9: SQL/Med Defines management of

external data - datalink type, abstract table, large BLOBs, federal DB support.

Will not be completed until late 2000 or early 2001.

Part 10:SQL/OLB Defines object language

binding for SQL - first binding is SQLJ

Part 5: SQL/Binding defines SQL binding to other

languages via ESQL and dynamic SQL.

Part 6: SQL/Transactions defines how database participate

in global transaction. Might be cancelled due to lack of

a need, DBMS vendors seems to be interfacing SQL with X/Open XA standard just fine.

Part 7:SQL/Temporal defines how SQL handles time-

series data, so that users are able to submit time as a variable.

New Technological Terms Triggers: special user-defined actions – usually in the form of stored

procedures, they are automatically invoked by the server based on the data-related events.

Roles: permissions (and privileges) that user assign to groups, not to individuals; users are assigned to roles so that they inherit the permissions and privileges that come with a role.

Persistent, implies that the “stored modules” are unlikely to come and go without specific application or administrative action, similar to persistent data in SQL systems

New Technological Terms

ORB (Object Request Broker) With an object server, the client/server application is written as a set of communicating objects. Client objects communicate with server objects using an Object Request Broker. The client invokes a method on a remote object. The ORB locates an instance of that object server class, invokes the requested method, and returns the results to the client object.

Java Bean: A component architecture that enables creation, assembly, and use of dynamic Java components. JavaBeans API defines a standard set of interfaces and behaviors that enable user to build reusable Java

New Technological Terms

ADO (ActiveX Data Objects): The architecture from Microsoft that users high-level components and objects for combining and creating applications. It is a set of component interfaces that allows developers to build both desktop applications and Web application.

OLE DB: Microsoft’s low-level interface to data across the organization. For more information, go to http://www.oledb.com

http://www.microsoft.com/data/oledb/oledb20/

Bibliography

Robert Orfali, Dan Harkey, Jeri Edwards. (1999) Client /Server Survivial Guide, Third Edition, Wiley.

Ryan K. Stephens and Ronald R. Plew, (1998) Teach Yourself SQL in 24 Hours, Sams Publishing.

Dan Chang, Dan Harkey, (1998) Client / Server Data Access with Java and XML, John Wiley & Sons, Inc.

Jim Melton (1998), SQL’s Stored Procedures, A Complete Guide to SQL/PSM, Morgan Kaufmann Publishers, Inc. San Francisco, California.