Download I got a request for ANSI SQL What is it and what do you

Help! I got a request for ANSI SQL
What is it and what do you do with it?
Presenter: Walter Guerrero
Computer Associates
Email: [email protected]
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 =
This is a
typical
a.emp_seq;
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 a
WHERE 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 JOIN
assignments a
ON 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_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;
_________________________________________________________
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_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
___________________________________________________
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?