20Copyright © 2008, Oracle. All rights reserved.
Globalization
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Objectives
After completing this lesson, you should be able to:
• Determine a correct database character set that meets your business requirements
• Obtain globalization support configuration information
• Customize language-dependent behavior for the database and individual sessions
• Specify different linguistic sorts for queries
• Retrieve data that matches a search string ignoring case or accent differences
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Globalization Support Features
• Language support
• Territory support
• Character set support
• Linguistic sorting
• Message support
• Date and time formats
• Numeric formats
• Monetary formats
French
data
Japanese
data
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What Every DBA Needs to Know
• What is a character set?
• How are character sets used?
• Problems to avoid
• Choosing your character set
• Obtaining character set information
• Specifying language-dependent behavior
• Using linguistic searching and sorting
• Using data conversion
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What Is a Character Set?
The Oracle database supports different classes of character-encoding schemes:
• Single-byte character sets– 7-bit– 8-bit
• Multibyte character sets, including Unicode
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Understanding Unicode
Supplementary characters
AL32UTF8 AL16UTF16
63
EE AA 9E
F0 9D 84 9E
64
C3
D0 A4
B6
á
t
d
ö
0063
00E1
0074
A89E
D834 DD1E
0064
00F6
0424
c
C3
74
91
Encoding: Representing characters with byte sequences
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How Are Character Sets Used?
• Oracle Net compares the client NLS_LANG setting to the character set on the server.
• If needed, conversion occurs automatically and transparently.
Client
Oracle Net
NLS_LANG
Server
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Problems to Avoid
Example:
No conversion occurs, because it does not seem to be required.
Issue: Invalid data are entered into the database.
ServerDatabase character set:
AL32UTF8
Client
Windows English
Code page: WE8MSWIN1252
NLS_LANG:
AL32UTF8 Oracle Net
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CREATE DATABASE ...CHARACTER SET US7ASCII NATIONAL CHARACTER SETUTF8 ...
% export NLS_LANG=‘SIMPLIFIED CHINESE_HONG KONG.ZHS16GBK’
Another Sample Problem
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Choosing Your Character Set
• Trade-offs to consider
• Choosing the correct character set that meets your business requirements now and in the future
• Specifying the character set
• Changing the character set after database creation
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Database Character Sets and National Character Sets
Database Character Sets National Character Sets
Defined at creation time Defined at creation time
Cannot be changed without re-creation (exceptions in certain configurations)
Can be exchanged
Store data columns of type CHAR, VARCHAR2, CLOB, LONG
Store data columns of type NCHAR, NVARCHAR2, NCLOB
Can store varying-width character sets
Can store Unicode using either AL16UTF16 or UTF8
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Obtaining Character Set Information
SQL> SELECT parameter, value 2 FROM nls_database_parameters
3 WHERE parameter LIKE '%CHARACTERSET%';
PARAMETER VALUE----------------------- -------------NLS_CHARACTERSET WE8ISO8859P1NLS_NCHAR_CHARACTERSET AL16UTF16
2 rows selected.
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SELECT sysdate FROM dual;
Initialization parameters for the database server
Environment variables for the clients
ALTER SESSION command
Specifying Language-Dependent Behavior
SQL function
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Specifying Language-Dependent Behavior for the Session
• Specify the locale behavior with the NLS_LANG environment variable:
– Language– Territory– Character set
• Set other NLS environment variables to:– Override database initialization parameter settings for all
sessions– Customize the locale behavior– Change the default location of the NLS library files
NLS_LANG=FRENCH_CANADA.WE8ISO8859P1
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Language-Dependent and Territory-Dependent Parameters
Parameter Default Values
NLS_LANGUAGE NLS_DATE_LANGUAGE NLS_SORT
AMERICAN AMERICAN BINARY
NLS_TERRITORY NLS_CURRENCY NLS_DUAL_CURRENCY NLS_ISO_CURRENCY NLS_DATE_FORMAT NLS_NUMERIC_CHARACTERS NLS_TIMESTAMP_FORMAT NLS_TIMESTAMP_TZ_FORMAT
AMERICA $ $ AMERICA DD-MON-RR ., DD-MON-RRHH.MI.SSXFF AM DD-MON-RRHH.MI.SSXFF AM TZR
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ALTER SESSION SET NLS_DATE_FORMAT='DD.MM.YYYY';
DBMS_SESSION.SET_NLS('NLS_DATE_FORMAT','''DD.MM.YYYY''') ;
Specifying Language-Dependent Behavior
Using NLS parameters in SQL functions:
SELECT TO_CHAR(hire_date,'DD.Mon.YYYY', 'NLS_DATE_LANGUAGE=FRENCH') FROM employeesWHERE hire_date > '01-JAN-2000';
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Linguistic Searching and Sorting
Sort order can be affected by:
• Case-sensitivity
• Diacritics or accent characters
• Combination of characters that is treated as a single character
• Phonetics or character appearance
• Cultural preferences
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Linguistic Searching and Sorting
Three types of sorting:
• Binary sorting– Sorted according to the binary values of the encoded
characters
• Monolingual linguistic sorting– A two-pass sort based on a character’s assigned major and
minor values
• Multilingual linguistic sorting– Based on the ISO standard (ISO 14651), and the Unicode 3.2
Standard for multilingual collation– Ordered by the number of strokes, PinYin, or radicals for
Chinese characters
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Using Linguistic Searching and Sorting
You can specify the type of sort used for character data with the:
• NLS_SORT parameter– Default value derived from the NLS_LANG environment
variable, if set– Can be specified for the session, client, or server
• NLSSORT function – Defines the sorting method at the query level
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Case-Insensitive and Accent-InsensitiveSearch and Sort
• Specify the linguistic name:
• Examples:
• Specify the sort action for WHERE clauses and PL/SQL blocks:
• Useful for migrated databases
NLS_SORT = <NLS_sort_name>[_AI | _CI]
NLS_SORT = FRENCH_M_AI
NLS_SORT = XGERMAN_CI
NLS_COMP = BINARY | ANSI
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Support in SQL and Functions
• The following SQL clauses support NLS_SORT and NLS_COMP settings:
– WHERE– ORDER BY– START WITH– HAVING– IN/NOT IN– BETWEEN– CASE-WHEN
• The NLSSORT() function supports the case-insensitive and accent-insensitive functionality.
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Linguistic Index Support
• Create an index on linguistically sorted values.
• Rapidly query data without having to specify ORDER BY clause and NLSSORT:
• Set the NLS_SORT parameter to match the linguistic definition that you want to use for the linguistic sort when creating the index.
CREATE INDEX list_word ON list (NLSSORT(word, 'NLS_SORT=French_M'));
SELECT word FROM list;
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Customizing Linguistic Searching and Sorting
You can customize linguistic sorting for:
• Ignorable characters
• Contracting or expanding characters
• Special combination letters or special letters
• Expanding characters or special letters
• Special uppercase and lowercase letters
• Context-sensitive characters
• Reverse secondary sorting
• Canonical equivalence
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Implicit Conversion Between CLOB and NCLOB
Transparent implicit conversion is supported in:
• SQL IN and OUT bind variables for query and DML
• PL/SQL functions and procedure parameter passing
• PL/SQL variable assignment
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NLS Data Conversion with Oracle Utilities
• Multiple data conversions can take place when data is exported from one database and imported into another if the same character sets are not used.
• External tables use the NLS settings on the server for determining the data character set.
• SQL*Loader:– Conventional path: Data is converted into the session
character set specified by NLS_LANG.– Direct path: Data is converted using client-side directives.
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NLS Data Conversion with Data Pump
• Data Pump Export always saves data in the same character set as the database from which the data originates.
• Data Pump Import converts the data to the character set of the target database, if needed.
• The Data Pump log file is written in the language specified by NLS_LANG for the session that started Data Pump.
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Language and Character Set File Scanner (LCSSCAN)
Character set
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Setting the Database Time Zone
The current time zone in the database is determined by the following:
• The SET TIME_ZONE clause of the CREATE DATABASE statement
• The time zone of the operating system on the database server host
• The time zone specified by the ALTER SESSION SET TIME_ZONE command
CREATE DATABASE ... SET TIME_ZONE='-04:00';
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Summary
In this lesson, you should have learned how to:
• Determine a correct database character set that meets your business requirements
• Obtain globalization support configuration information
• Customize language-dependent behavior for the database and individual sessions
• Specify different linguistic sorts for queries
• Retrieve data that matches a search string ignoring case or accent differences
Copyright © 2008, Oracle. All rights reserved.20 - 36
Practice 20 Overview: Using Globalization Support
This practice covers the following topics:
• Determining the database character set
• Setting the NLS_SORT variable