ORACLE 讀寫 string longer than 4000 問題

• ORA-01704: string literal too long
  *Cause:  The string literal is longer than 4000 characters.(寫入字串超過4000)
  *Action:  Use a string literal of at most 4000 characters. Longer values may only be entered using bind variables.(需使用變數裝載，再放到 insert sql中)

• Ora-01489: result of string concatenation is too long
  *Cause: String concatenation result is more than the maximum size.(回傳值字串超過欄位規格)
  *Action: Make sure that the result is less than the maximum size.
  * select TO_CLOB(listagg(a,'_') WITHIN GROUP (ORDER BY sn )) from table;
  *在 CI +某個PHP版本，接收 CLOB 出現 json_encode 問題
  error_reporting(0);
  $query = $this->db->get();
  $data = $query->result_array();
  $data[0]['IM_CONTENT']->read($data[0]['IM_CONTENT']->size());

在資料庫設定為 utf8的環境下

varchar2(10 char)<=可以同時塞10個中文字

varchar2(10 byte)<=可以同時塞3個中文字，一個英文字

varchar2(10)<=可以同時塞3個中文字，一個英文字

http://cch8.blogspot.tw/2010/12/varchar2.html

lengthb(string)計算string所佔的byte長度
length(string)計算string所佔的char長度
ps.可以用length(string)=lengthb(string)判斷字符串是否含有中文。
http://blog.csdn.net/gavinvong/article/details/9101479