View in Oracle to display rows from last weekday

Question

I need to make a view in Oracle that will display all rows from last weekday.

So for Tuesday it should be like this cause I need all entries from Monday:

select * from table_1 where to_char(Mydate,'yyyy-mm-dd') =  to_char(sysdate-**1**,'yyyy-mm-dd');

But if it is Monday then I need all entries from Friday.

select * from table_1 where to_char(Mydate,'yyyy-mm-dd') =  to_char(sysdate-**3**,'yyyy-mm-dd');       

How can I make one view that will always display correct rows from last weekday?

Answer 1

SELECT  *
FROM    table_1
WHERE   mydate >= SYSDATE - CASE WHEN TO_CHAR(SYSDATE, 'D') > 6 THEN 3 ELSE 1 END
        AND mydate < SYSDATE - CASE WHEN TO_CHAR(SYSDATE, 'D') > 6 THEN 3 ELSE 1 END + 1

Answer 2

Hi Imageree,

You could use CASE:

SQL> WITH table_1 AS
  2  (SELECT SYSDATE - 20 + ROWNUM mydate FROM dual CONNECT BY ROWNUM <= 40)
  3  SELECT *
  4    FROM table_1
  5   WHERE trunc(Mydate) =
  6           CASE WHEN to_char(SYSDATE, 'D') = to_char(DATE '2000-01-02', 'D')
  7              THEN -- sunday
  8              trunc(SYSDATE - 2)
  9           WHEN to_char(SYSDATE, 'D') = to_char(DATE '2000-01-03', 'D')
 10              THEN -- monday
 11              trunc(SYSDATE - 3)
 12           ELSE
 13              trunc(SYSDATE - 1)
 14           END;

MYDATE
-----------
08/01/2010

Note: Depending upon your NLS setting, to_char(X, 'D') may return 1 for mondays or sundays. Relying on a known monday (eg: 2000-01-03 in my case) will make this query work in any setting.