plqsl 复制 vlookup

Question

My query returns the following table:

|  CODE  |    DATE    |  VALUE  |
|  123   | 30/06/2012 |   11    |
|  231   | 01/07/2012 |   22    |
|  321   | 02/07/2012 |   11    |
|  234   | 03/07/2012 |   11    |

I need it to create a column based off of the DATE and VALUE column. So it must take todays value ad divide it by the previous days

So once the query runs the result should be:

|  CODE  |    DATE    |  VALUE  |  RET  |
|  123   | 30/06/2012 |   11    |       |
|  231   | 01/07/2012 |   22    |  2.0  |
|  321   | 02/07/2012 |   11    |  0.5  |
|  234   | 03/07/2012 |   11    |  0.0  |

This is as far as I have got:

SELECT
    CODE
    DATE
    VALUE 
    (DATE/(TO_DATE(DATE)-1)) AS RET
FROM
    ....

But obviously you can't divide a date by another date and expect to get a number.

Thanks

Answer 1

To be able to access previous value of a column you can use lag analytical function:

   -- sample of data from your question
   SQL> with t1(CODE, DATE1, VALUE1) as(
      2    select 123, to_date('30/06/2012', 'dd/mm/yyyy'), 11  from dual union all
      3    select 231, to_date('01/07/2012', 'dd/mm/yyyy'), 22  from dual union all
      4    select 321, to_date('02/07/2012', 'dd/mm/yyyy'), 11  from dual union all
      5    select 234, to_date('03/07/2012', 'dd/mm/yyyy'), 11  from dual
      6  )-- the query
      7  select code
      8       , Date1
      9       , Value1
     10       , to_char(value1 / lag(value1, 1) over(order by date1), '999990.0') ret
     11    from t1
     12  ;

Result:

      CODE DATE1           VALUE1      RET
---------- -----------   ----------   ---------
       123 30/06/2012         11 
       231 01/07/2012         22       2.0
       321 02/07/2012         11       0.5
       234 03/07/2012         11       1.0