Oracle SQL: Get the last eight months of data (with YEAR and MONTH columns)

I have a table that has columns YEAR and MONTH, which are varchars, which have a format like MONTH = '02开发者_开发问答', YEAR = '2011'.

What query can I use to get the last eight months of data, excluding the current month?

Try

where to_date(year || month, 'YYYYMM') 
       between add_months(trunc(sysdate, 'MM'), -8) and trunc(sysdate) 

Try this:

SELECT *
  FROM myTable 
WHERE (year, month) IN
(
SELECT TO_CHAR(ADD_MONTHS(SYSDATE, -level), 'RRRR') AS year, 
  TO_CHAR(ADD_MONTHS(SYSDATE, -level), 'MM') AS month
  FROM dual
  CONNECT BY LEVEL < 8
)

Another version:

SELECT *
  FROM myTable 
WHERE year||month IN
(
SELECT TO_CHAR(ADD_MONTHS(SYSDATE, -level), 'RRRRMM') AS yearmonth
  FROM dual
  CONNECT BY LEVEL < 8
)

Best I can think of is this:

SELECT * FROM table WHERE (MONTH || YEAR) IN ('012011','122010', et cetera)

It is a brute force method, so it is not feasible if you want your query to generalize.