Oracle is a commonly used database management system, but garbled characters are often encountered when using it. Garbled characters not only affect the accuracy of the data, but also cause trouble in our work. This article will introduce the reasons and solutions for Oracle displaying garbled characters.

1. Reasons for garbled characters

1. Incorrect database encoding

When establishing a database, you need to set the database character set and proofreading set. If the settings are incorrect, the database may be garbled. Under normal circumstances, we will choose UTF-8 encoding because it supports multiple languages ​​and is less prone to garbled characters. But if other encodings are set, garbled characters may appear.

2. Incorrect client encoding

If the encoding of the client and the database are inconsistent, garbled codes may easily occur. For example, the database is UTF-8 encoded, but the client is GBK encoded. When entering data on the client, garbled characters appear.

3. The database character set is inconsistent with the operating system character set

If the database character set is inconsistent with the operating system character set, garbled characters may easily occur. For example, on a Windows system, the operating system character set is GB2312, but the database character set is UTF-8, then garbled characters may occur.

2. Solution

1. Modify the database character set

If the database character set is incorrectly set, it can be solved by modifying the database character set. However, this approach requires caution, as modifying the character set can cause some data to be corrupted. Therefore, before making modifications, you need to back up the data in the database.

The modification method is as follows:

(1) Check the database character set and proofreading set

First, we need to check the database character set and proofreading set:

SELECT * FROM V$NLS_PARAMETERS WHERE PARAMETER IN ('NLS_CHARACTERSET', 'NLS_NCHAR_CHARACTERSET');

After running the above code, the character set and collation set of the database will be displayed. If it is not UTF-8 encoding, it needs to be modified.

(2) Back up data

Before making modifications, you need to back up the data in the database to prevent data loss during the modification process.

(3) Stop the database

Before modifying the database character set, you need to stop the database first. You can use the following command to stop the database:

SQL> SHUTDOWN IMMEDIATE;

(4) Modify the character set

After closing the database, modify the character set:

SQL> STARTUP MOUNT;
SQL> ALTER SYSTEM ENABLE RESTRICTED SESSION;
SQL> ALTER SYSTEM SET JOB_QUEUE_PROCESSES=0;
SQL> ALTER SYSTEM SET AQ_TM_PROCESSES=0;
SQL> ALTER DATABASE OPEN;
SQL> ALTER DATABASE CHARACTER SET INTERNAL_USE utf8;

After the modification is completed, the database needs to be restarted.

2. Modify the client encoding

If the encoding of the client and the database are inconsistent, you can modify the encoding on the client. If you are using a tool such as PL/SQL Developer, you can modify the encoding in the tool options. If you use a programming language such as Java to connect to the database, encoding settings need to be made in the code. For example, to connect to the database in Java code, you need to set the following code:

jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8

3. Modification operation System character set

If the database character set is inconsistent with the operating system character set, the operating system character set needs to be modified. On Linux systems, you can use the locale command to modify the character set:

View the current character set

locale

Modify the character set

localedef -c - f UTF-8 -i zh_CN zh_CN.UTF-8

After the modification is completed, remember to restart the service.

Summary

Garbled characters are a problem we often encounter when using Oracle to manage databases. There are many reasons for garbled characters, but the main reasons are incorrect database encoding, incorrect client encoding, and inconsistent database character sets and operating system character sets. Methods to solve the problem include modifying the database character set, modifying the client encoding, and modifying the operating system character set. It should be noted that data needs to be backed up before modification to avoid data loss.

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