Because of importing the database file a few days ago, it has been unsuccessful to import, because when I install oracle, my code chooses UTF-8, and a text is stored in 3 bytes, which leads to a lot of data confusion and the length of the field. Modify the code after GBK to solve the problem. The following is a summary of commands when modifying encoding.

First of all, it is recommended to modify the encoding of plsql, modify the environment variables, right-click on my computer to click properties, and then enter the advanced system settings.

NLS_LANG
SIMPLIFIED CHINESE_CHINA.ZHS16GBK

Next, open the cmd black window: execute in turn.

SQL> set ORACLE_SID=The one you want to enter the database sid，Mine is orcl
SQL> sqlplus /nolog

SQL> conn /as sysdba
Connected. 

SQL> shutdown immediate; 
Database closed. 
Database dismounted. 
ORACLE instance shut down. 

SQL> startup mount
Total System Global Area  236000356 bytes 
Fixed Size                   451684 bytes 
Variable Size             201326592 bytes 
Database Buffers           33554432 bytes 
Redo Buffers                 667648 bytes 
Database mounted.

SQL> ALTER SYSTEM ENABLE RESTRICTED SESSION;
System altered. 

SQL> ALTER SYSTEM SET JOB_QUEUE_PROCESSES=0;
System altered. 

SQL> ALTER SYSTEM SET AQ_TM_PROCESSES=0;
System altered. 

SQL> alter database open;
Database altered. 

SQL> ALTER DATABASE CHARACTER SET ZHS16GBK;
ALTER DATABASE CHARACTER SET ZHS16GBK 
* 
ERROR at line 1: 
ORA-12712: new character set must be a superset of old character set
//Hint our character set: The new character set must be a superset of the old character set, at which time we can skip the checking of the superset to make changes:

SQL> ALTER DATABASE character set INTERNAL_USE ZHS16GBK;
Database altered.

SQL> select * from v$nls_parameters;
//slightly 
19 rows selected. 

SQL> shutdown immediate; 
Database closed. 
Database dismounted. 
ORACLE instance shut down. 

SQL> startup
ORACLE instance started. 
Total System Global Area  236000356 bytes 
Fixed Size                   451684 bytes 
Variable Size             201326592 bytes 
Database Buffers           33554432 bytes 
Redo Buffers                 667648 bytes 
Database mounted. 
Database opened.