CLOB in an ASCII characterset database contains non-ASCII characters - how?

Question

I am working with an Oracle 12.2 database. The database characterset is WE8MSWIN1252 (ie. an ASCII characterset).

The database contains a table with a CLOB column (according to Oracle SQL Developer). Some values in this column contain non-ASCII characters (I know this as when using ASCIISTR function on this column I can see the escaped non-ASCII character codes).

How is this possible? I thought ASCII characterset databases could only store unicode in NVARCHAR, NCLOB etc.

(I only discovered this when I was using a linked server to the Oracle db from SQL Server - when I ran an OPENQUERY on the table with the CLOB, it returned ? for the non-ASCII characters. I changed the OPENQUERY query string to use TO_NCLOB(clob_column) and it returned the non-ASCII characters.)

Any ideas?

Thanks

Answer 1

From wikipedia WE8MSWIN1252 description: Windows-1252 or CP-1252 (code page 1252) is a single-byte character encoding of the Latin alphabet, used by default in the legacy components of Microsoft Windows for English and many European languages including Spanish, French, and German.

So, it a CLOB in a database with this charset can store strings like éàè. And ASCIISTR returns escaped codes because these chars are not defined in ASCII, for example:

SQL> select asciistr('é') eaccent, asciistr('e') e from dual;

EACCENT    E
---------- -
\FFFD\FFFD e