Dear gurus: Can u pls explain the difference between VARCHAR2 & NVARCHAR2?

Dear gurus,

Can you please explain in simple terms we beginners the difference between VARCHAR2 and NVARCHAR2.

I have read all the documentation, but I just don't understand?

What exactly is the advantage of NVARCHAR2?

When should we use it?

What are the differences?

NVARCHAR2 is used only when using non-English characters sets?

Is there a saving advantage?

Some say that NVARCHAR2 will give different VARCHAR2 columns values when you use the LENGTH function?

Thanks in advance

Published by: user12240205 on October 27, 2011 06:15

Published by: user12240205 on October 27, 2011 06:15

CHAR (CHAR, VARCHAR2, LONG, CLOB) data types store data in the database character set. NCHAR (NVARCHAR2, NCHAR, NCLOB) data types store data in the national character set. The national character set can be either AL16UTF16 (the default) or UTF8 (rare compatibility requirements). The database character set can be one of the dozens of characters supported by Oracle games. The recommended database charset is AL32UTF8.

AL16UTF16 and are all two AL32UTF8 Unicode - UTF-16BE and UTF-8 encodings, proportionally.

The benefits of the NCHAR data types:

-They are guaranteed to Unicode data types, in other words, any database from Oracle 9.0 can store Unicode data into NCHAR, NVARCHAR2, and NCLOB columns.
-Storage Unicode languages of South and East Asia is more compact in relation to AL32UTF8 AL16UTF16. AL16UTF16 storage is only possible in NCHAR data types.

(Serious!) cons of NCHAR data types:

-You need a special coding in client access API to ensure that the data you want to store NCHAR data type columns is not through conversion to character data, lose the advantage 'warranty Unicode.
-There are Oracle components that do not support the data types NCHAR, including Oracle Text and XDB.
-It's confusing and prone to work with two character sets of database, the database character set and the national character set.
-Storage of most European languages is more compact in AL32UTF8 compared to AL16UTF16.

Advice from the Oracle:

-For any new database, create it with the character AL32UTF8 and forget types NCHAR data.
-For all existing applications to make multilingual, migrate the database backend to AL32UTF8 and forget the NCHAR data types.
-For any database existing non-Unicode serving a large legacy application system that is too expensive or impossible migrate to Unicode, you are invited to add a minor module which must support multilingual data and for which a separate database makes little sense, you can consider NVARCHAR2 columns for these multilingual data.

-Sergiusz

Tags: Database

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