Oracle SQL，在select语句中获取长度更大的varchar2列

Question

I have a varchar2(8) column in a table, and I want to convert it to varchar2(100) in the select statement (ie I don't want to to call an "alter table" afterwards).* Is it possible? Is there some function like "to_varchar2(x, 100)"?

(*) the reason is that I need to use the column in a "model" statement, where there will be additional identifiers that are longer. I don't want to create an intermediate table and use "alter table" to change the varchar2 length. Example:

  select date, mystringvariable r, somenumber v from MyTable
  model
  unique single reference
  return updated rows   
  partition by(date) dimension by(r) measures(v)
  rules upsert automatic order ( 
  v['too_long_identifier']  = v['X1']
  );

     Error at line 5:

     ORA-12899: value too large for column ??? (actual: 19, maximum: 8)
          partition by(date) dimension by(r) measures(v)
                                          ^

Answer 1

不确定您需要在查询中的哪个位置执行此操作（我没有要测试的数据），但是如果str是数据类型为varchar2(8)任何表达式并且您需要将其重新转换为varchar2(100) ，则可以使用cast功能：

 .... cast(str as varchar2(100)) ....