查clob内容
select dbms_lob.substr(c_content) from table_content t where cond='***'
dbms_lob.substr将大文本转换字符类型读出来.
dbms_lob.subs的转换对字段content的内容大小有限制～！一般几十k就已经超出了～！
改clob内容
update table_content set c_content = replace(c_content,'629107','992277') where cond = ***;//替换字段中内容
update table_content set c_content = 'Singapore 629107' where cond= ***;设置字段的值