Oracle DB程序员：如何识别表中的双字节字符数据？

Question

Hi Oracle sql programmers, how do you identify double byte character in the db which I mean to find all the data in column 1 in table1 which contain double byte character such as Chinese character(s)?

UPDATE 1: I don't even know what Chinese characters would be in the column, I just need to find all the first_name and last_name columns which users entered any non-English characters, then change the value to NA.

Answer 1

The simplest option assuming you truly mean non-English (ie any character not in the US7ASCII character set) would be something like

UPDATE table_name
   SET first_name = 'NA'
 WHERE length( first_name ) != lengthb( first_name )

LENGTH returns the length of a string in characters while LENGTHB returns the length of a string in bytes. UTF-8 encodes the US7ASCII characters with a single byte. If there are any non-US7SACII characters, the length in bytes will be greater than the length in characters.

Answer 2

I've never tried this, but I guess you could convert each character to a number and look for values over 256:

SQL> select ascii(unistr('\53f0')) from dual;

ASCII(UNISTR('\53F0'))
----------------------
                 21488