Help! I got a request for ANSI SQL

What is it and what do you do with it?

Presenter: Walter Guerrero

Computer Associates Email: walter.guerrero@ca.com

Abstract

As companies deploy more XML and exchange information across many different database types, they will need to implement ISO standards within their business models.

SQL statements must then move away from proprietary format and fit within the ISO/ANSI standards. These ISO/ANSI standards provide a more readable and portable format that can be used by different database engines. Oracle is making the move for Oracle developers to start using ISO/ANSI SQL constructs in the creation of SQL statements to exchange data between XML style sheets. Even after changing the SQL statements into the ISO/ANSI format, developers still need to be concern with the performance needs of the SQL statements running in an Oracle database server.

What is ANSI/ISO SQL

• ANSI and ISO SQL is the standard definition of SQL as agreed by these standards bodies

• ANSI and ISO SQL standards are the same

• If more information is desired, visit • http://www.cssinfo.com/ncitsgate.html

• http://www.iso.ch/

Old Syntax Issues

• Non-standard implementations

• Lack of data modeling

• Lack of data structure processing

• Outer join implementations not standardized

Benefits of ANSI/ISO SQL

• Portability of SQL code across different database engines

• Easier to read SQL statements

• National language support included

Benefits Of ANSI/ISO SQL – Cont’d

• Standardize outer join implementations

• No need to use a UNION to complete an outer join process

Outer Join Advanced Capabilities

• Database navigation

• Access Optimizations

• Data warehouse interaction

• Flexible aggregate operations usage

• Object relational interaction

• View update capability

• Multimedia directory support

Why ANSI/ISO SQL

• Allows the Oracle SQL statements to become more portable and readable

• Information exchange between companies requires portable code

• This is very important for companies using XML, which uses SQLX or XSQL

Oracle Supported ANSI/ISO Datatypes

• Character, char, nchar

• Varchar

• National

• Decimal, dec

• Integer, int

• Float

• Double, precision

• Real

Basic ANSI/ISO SQL Keywords

• Inner

• Using

• Natural

• Left Outer – outer is optional

• Right Outer – outer is optional

• Full Outer – outer is optional

• Case

Advanced ANSI/ISO SQL Keywords

• Siblings• Cross• When/then/else• Extract• Analytic functions• IS OF• Cast• First• Last

Standard Oracle SQL Join Keywords

• =

• =(+)

• (+)=

• Full outer is made up of either =(+) or (+)= and an UNION to an equi-join

Typical Oracle Statement

SELECT *

FROM employees e,

assignments a

WHERE e.emp_seq =

a.emp_seq

This is a typical inner

join using Oracle syntax

Basic ANSI/ISO SQL Statement

SELECT *

FROM employees e JOIN

assignments a

ON e.emp_seq =

a.emp_seq;This is a typical

ANSI SQL inner join

ANSI/ISO SQL “USING” Statement

SELECT *

FROM employees e JOIN

assignments a USING

(emp_seq);

ANSI/ISO SQL “Natural” Statement

SELECT *

FROM employees e

NATURAL JOIN

assignments a;

Oracle Syntax Outer Join

SELECT *

FROM employees e,

assignments a

WHERE e.emp_seq =

a.emp_seq(+)

ANSI Syntax Left Outer Join

SELECT *

FROM employees e LEFT

OUTER JOIN assignments a

ON e.emp_seq = a.emp_seq

ANSI Syntax Right Outer Join

SELECT *

FROM employees e RIGHT

OUTER JOIN assignments a

ON e.emp_seq = a.emp_seq

Oracle Syntax Full Outer Join

SELECT e.emp_seq, p.proj_seq

FROM employees e, assignments a,

projects p

WHERE e.emp_seq = a.emp_seq(+)

AND a.proj_seq = p.proj_seq(+)

UNION ALL

SELECT null, p.proj_seq

FROM projects p, assignments a

WHERE p.proj_seq = a.proj_seq(+)

AND a.proj_seq IS NULL

ANSI/ISO Syntax Full Outer Join

SELECT e.emp_seq, p.proj_seq

FROM (employees e LEFT

JOIN assignments a ON

e.emp_seq = a.emp_seq)

FULL JOIN projects p

ON a.proj_seq = p.proj_seq

Oracle Decode Syntax

SELECT d.dept_seq, d.description,

decode(d.active,

'Y','Active',

'N','Not Active',

'Not Applicable')

FROM departments d

ANSI/ISO CASE Syntax

SELECT d.dept_seq, d.description,

CASE active

WHEN 'Y' THEN 'Active'

WHEN 'N' THEN 'Not Active'

ELSE 'Not applicable' END

FROM departments d

Oracle Inner Syntax Performance Example

SELECT *FROM employees e, assignments aWHERE e.emp_seq = a.emp_seq______________________________________

SELECT STATEMENT Cost = 17 HASH JOIN TABLE ACCESS FULL ASSIGNMENTS TABLE ACCESS FULL EMPLOYEES

ANSI/ISO Inner Syntax Performance Example

SELECT * FROM employees e JOINassignments aON e.emp_seq = a.emp_seq;_________________________

SELECT STATEMENT Cost = 17 HASH JOIN TABLE ACCESS FULL ASSIGNMENTS TABLE ACCESS FULL EMPLOYEES

Oracle Syntax Outer Join Performance Example

SELECT e.emp_seq, p.proj_seqFROM employees e, assignments a,projects pWHERE e.emp_seq = a.emp_seq(+)AND a.proj_seq = p.proj_seq(+)UNION ALLSELECT null, p.proj_seqFROM projects p, assignments aWHERE p.proj_seq = a.proj_seq(+)AND a.proj_seq IS NULL;_________________________________________________________SELECT STATEMENT Cost = 6 UNION-ALL NESTED LOOPS OUTER HASH JOIN OUTER INDEX FULL SCAN PK_EMP INDEX FULL SCAN PK_ASSIGN INDEX UNIQUE SCAN PK_PROJECTS FILTER HASH JOIN OUTER INDEX FULL SCAN PK_PROJECTS INDEX FULL SCAN PK_ASSIGN

ANSI/ISO Syntax Outer Join Performance Example

SELECT e.emp_seq, p.proj_seqFROM (employees e LEFT JOIN assignments a ON e.emp_seq =

a.emp_seq)FULL JOIN projects pON a.proj_seq = p.proj_seq___________________________________________________

SELECT STATEMENT Cost = 4 VIEW UNION-ALL NESTED LOOPS OUTER HASH JOIN OUTER INDEX FULL SCAN PK_EMP INDEX FULL SCAN PK_ASSIGN INDEX UNIQUE SCAN PK_PROJECTS INDEX FULL SCAN PK_PROJECTS FILTER NESTED LOOPS OUTER INDEX FULL SCAN PK_EMP INDEX FULL SCAN PK_ASSIGN

Performance Differences

• There are slight performance differences between Oracle and ANSI SQL syntaxes

• ANSI SQL provides you with improved readability

• ANSI SQL provides you with code portability across different database systems

Summary

• Now that Oracle supports ANSI SQL 92 and parts of ANSI SQL 99, it is important to keep performance targets in mind

• Do performance analysis of your ANSI/ISO SQL during your development phase

• Use the CBO (Cost Based Optimizer) to your advantage

Questions?