Condition in WHERE clause (Oracle) - sql

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, i.e. 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;