在Oracle中以日期格式转换varchar字段数据

Question

I have table test column has cretaed_dt and id.Both are varchar 2 type.

desc test

ID Varchar2(30)
Created_Dt varchar2(30)

select * from test

ID       created_dt
1        2014-07-22-12.23.49.832868
2        2014-08-04-19.40.11.787317
3        2014-06-15-19.40.11.787317

I need to pick the data between 21st July to 5th aug 2014.Idealy ID 1 and 2 need to pick.

I am not able to do this because created date column is in varchar2.

Please assist.

Answer 1

Although your data is stored as varchar2() , you can still use it. Happily the strings are in the right format for comparison operations. So:

where created_dte >= '2014-07-21' and created_dte < '2014-08-05'

You can convert the varchar2() to a date using to_date() . However, just using the string as is allows Oracle to take advantage of an index on the column.

Although you can do what you want, you should store date/times in native date format in the database. Oracle has a wealth of date-related functions that are then accessible.

Answer 2

Use this:

with t as (
  select '1' id, '2014-07-22-12.23.49.832868' created_dt from dual union all
  select '2' id, '2014-08-04-19.40.11.787317' created_dt from dual union all
  select '3' id, '2014-06-15-19.40.11.787317' created_dt from dual 
)
select * 
  from t
 where to_timestamp(created_dt, 'yyyy-MM-dd-HH24.MI.SS.FF') between to_date('21 jul 2014', 'DD mon YYYY') and to_date('5 aug 2014', 'DD mon YYYY')