How to perform character set conversion in oracle

Oracle character set conversion

When using Oracle database, sometimes it is necessary to convert between character sets. For example, when the source database character set does not support certain characters, they need to be converted to the target character set for correct storage and processing.

Oracle provides several methods for character set conversion. Two commonly used methods will be introduced below: exp/imp and ALTER DATABASE CHARACTER SET.

Method 1: Use exp/imp for character set conversion

The exp and imp commands are Oracle database backup and recovery tools and can also be used for character set conversion.

The steps are as follows:

1. Use exp to export the data in the source database (exp can specify the character set):

exp username/password@source_db file=exp_file. dmp log=exp_file.log charset=source_charset

Among them, source_charset is the character set of the source database, which can be queried through the following statement:

SELECT parameter, value
FROM NLS_DATABASE_PARAMETERS
WHERE parameter IN ('NLS_CHARACTERSET', 'NLS_NCHAR_CHARACTERSET');

2. Convert the exported data file to the target character set:

iconv -f source_charset -t target_charset exp_file.dmp > conv_exp_file.dmp

Among them, the iconv command is a commonly used character set conversion tool under Linux. source_charset and target_charset are the character sets of the source database and target database respectively.

3. Use imp to import the converted data into the target database:

imp username/password@target_db file=conv_exp_file.dmp log=imp_file.log

This is done Character set conversion.

Method 2: Use ALTER DATABASE CHARACTER SET for character set conversion

Use the ALTER DATABASE CHARACTER SET command to convert character sets directly in the Oracle database.

The steps are as follows:

1. Back up the database

Be sure to back up the database before performing character set conversion.

2. Stop the database

Use the SHUTDOWN command to stop the database.

3. Modify the character set

Use the ALTER DATABASE CHARACTER SET command to convert the character set. For example, convert the character set GBK of the source database to the character set UTF8 of the target database:

ALTER DATABASE CHARACTER SET UTF8;

4. Modify the configuration file

Modify $ORACLE_HOME /network/admin/tnsnames.ora file, change the character set of the source database to the character set of the target database.

5. Start the database

Use the STARTUP command to start the database.

6. Reload the data into the database

Use imp to re-import the data into the target database.

Summary:

The above are two commonly used Oracle character set conversion methods. Necessary backup must be made before use to prevent data loss or unexpected problems.

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