International storage

Question

Hello,
I had store the chinese character using
nvarchar2 in Oracle9i using UTF-16 encoding
(NLS_NCHAR_CHARACTERSET = AL16UTF16 )
The problem is how i can i read the
chinese character using SQLPlus or iSQLPlus ?
When i select the field, it display "???"
I had try to set nls_language = "Chinese Traditional"
and using convert(zh,"AL16UTF16","UTF8") in SQL
but no use ...
Thx
Kenny Mak

Answer 1

Mak,
You need to use the setFormofUSe in order for your data to get loaded correctly. I am cutting this out of the globalization guide (which you should read):
Binding and Defining Java Strings to SQL NCHAR Datatypes
For binding or defining Java string variables to SQL NCHAR datatypes, Oracle
provides an extended PreparedStatement which has the setFormOfUse()
method through which you can explicitly specify the target column of a bind
variable to be a SQL NCHAR datatype. The following code illustrates how to bind a
Java string to an NCHAR column.
int employee_id = 12345;
String last_name = "Joe"
oracle.jdbc.OraclePreparedStatement pstmt =
(oracle.jdbc.OraclePreparedStatement)
conn.prepareStatement("INSERT INTO employees (last_name, employee_id)
VALUES (?, ?)");
pstmt.setFormOfUse(1, oracle.jdbc.OraclePreparedStatement.FORM_NCHAR);
pstmt.setString(1, last_name);
pstmt.setInt(2, employee_id);
pstmt.execute(); /* execute to insert into first row */
employee_id += 1; /* next employee number */
last_name = "\uFF2A\uFF4F\uFF45"; /* Unicode characters in name */
pstmt.setString(1, last_name);
pstmt.setInt(2, employee_id);
pstmt.execute(); /* execute to insert into second row */
You can define the target SQL NCHAR columns by specifying their datatypes, forms
of use, and lengths. JDBC uses this information to optimize the performance of
fetching SQL NCHAR data from these columns. The following is an example of
defining a SQL NCHAR column.
OraclePreparedStatement pstmt = (OraclePreparedStatement)
conn.prepareStatement("SELECT ename, empno from emp");
pstmt.defineColumnType(1,Types.VARCHAR, 3,
OraclePreparedStatement.FORM_NCHAR);
pstmt.defineColumnType(2,Types.INTEGER);
ResultSet rest = pstmt.executeQuery();
String name = rset.getString(1);
int id = reset.getInt(2);
To define a SQL NCHAR column, you need to specify the datatype that is equivalent
to a SQL CHAR column in the first argument, the length in number of characters in
the second argument, and the form of use in the fourth argument of
defineColumnType().
You can bind or define a Java string against an NCHAR column without explicitly
specifying the form of use argument. This implies the following:
If you do not specify the argument in the setString() method, then JDBC
assumes that the bind or define variable is for the SQL CHAR column. As a
result, it tries to convert them to the database character set. When the data gets
to the database, the database implicitly converts the data in the database
character set to the national character set. During this conversion, data can be
lost when the database character set is a subset of the national character set.
Because the national character set is either UTF8 or AL16UTF16, data loss
would happen if the database character set is not UTF8 or AL32UTF8.
Because implicit conversion from SQL CHAR to SQL NCHAR datatypes happens
in the database, database performance is degraded.
In addition, if you bind or define a Java string for a column of SQL CHAR datatypes
but specify the form of use argument, then performance of the database is
degraded. However, data should not be lost because the national character set is
always a larger set than the database character set.
You need to set your NLS_LANG on the middle tier or client where you set up iSQL*PLUS.