WHERE子句中的条件（Oracle）

Question

I need a query which returns data based on what month/year it is. Below is a subquery i wrote which returns one row - start_date and end_date are the values i need to use in my main query

WITH SUBQ AS (SELECT 
    dim.MONTH_NAME as current_month_name
   ,dim.year_period as current_month
   ,dim.PERIOD_YEAR as YEAR
   ,CASE WHEN dim.year_period NOT LIKE '%01' THEN to_number(CONCAT(to_char(dim.PERIOD_YEAR-1) , '01' ))
         WHEN dim.year_period LIKE '%01'THEN to_number(CONCAT(to_char(dim.PERIOD_YEAR-2) , '01' ))
         END AS START_DATE 
   ,CASE WHEN dim.year_period NOT LIKE '%01' THEN to_number(CONCAT(to_char(dim.PERIOD_YEAR) , '01'  ))
         WHEN dim.year_period LIKE '%01'THEN to_number(CONCAT(to_char(dim.PERIOD_YEAR-1) , '01'   )) END AS ENDDATE 
  from dim_periods dim    WHERE dim.year_period=to_number(to_char(sysdate, 'YYYYMM')))

Question is - how do i use values from subquery with one row in where clauses? I need to get something like this, i just dont understand how should i join my subquery and the rest of the tables i use -

select * from financial_data fd 
where fd.year_period BETWEEN subq.start_date and subq.enddate

Answer 1

You could join the subquery , ie the CTE with the table, and then use the column name in the filter predicate . The result of the subquery in the WITH clause acts like a temporary table .

For example,

WITH SUBQ AS
  (SELECT dim.MONTH_NAME AS current_month_name ,
    dim.year_period      AS current_month ,
    dim.PERIOD_YEAR      AS YEAR ,
    CASE
      WHEN dim.year_period NOT LIKE '%01'
      THEN to_number(CONCAT(TO_CHAR(dim.PERIOD_YEAR-1) , '01' ))
      WHEN dim.year_period LIKE '%01'
      THEN to_number(CONCAT(TO_CHAR(dim.PERIOD_YEAR-2) , '01' ))
    END AS START_DATE ,
    CASE
      WHEN dim.year_period NOT LIKE '%01'
      THEN to_number(CONCAT(TO_CHAR(dim.PERIOD_YEAR) , '01' ))
      WHEN dim.year_period LIKE '%01'
      THEN to_number(CONCAT(TO_CHAR(dim.PERIOD_YEAR-1) , '01' ))
    END AS ENDDATE
  FROM dim_periods dim
  WHERE dim.year_period=to_number(TO_CHAR(SYSDATE, 'YYYYMM'))
  )
SELECT fd.COLUMNS,
  q.COLUMNS
FROM financial_data fd
JOIN subq q
ON (fd.KEY = q.KEY) -- join key
WHERE fd.year_period BETWEEN q.start_date AND q.enddate;

So, SUBQ acts like a temporary table, which you join with financial_data table.

UPDATE OP doesn't want the ANSI join syntax .

WITH SUBQ AS
  (SELECT dim.MONTH_NAME AS current_month_name ,
    dim.year_period      AS current_month ,
    dim.PERIOD_YEAR      AS YEAR ,
    CASE
      WHEN dim.year_period NOT LIKE '%01'
      THEN to_number(CONCAT(TO_CHAR(dim.PERIOD_YEAR-1) , '01' ))
      WHEN dim.year_period LIKE '%01'
      THEN to_number(CONCAT(TO_CHAR(dim.PERIOD_YEAR-2) , '01' ))
    END AS START_DATE ,
    CASE
      WHEN dim.year_period NOT LIKE '%01'
      THEN to_number(CONCAT(TO_CHAR(dim.PERIOD_YEAR) , '01' ))
      WHEN dim.year_period LIKE '%01'
      THEN to_number(CONCAT(TO_CHAR(dim.PERIOD_YEAR-1) , '01' ))
    END AS ENDDATE
  FROM dim_periods dim
  WHERE dim.year_period=to_number(TO_CHAR(SYSDATE, 'YYYYMM'))
  )
SELECT fd.COLUMNS,
  q.COLUMNS
FROM financial_data fd,
  subq q
WHERE fd.KEY = q.KEY -- join key
AND fd.year_period BETWEEN q.start_date AND q.enddate;