sysdate-7
SELECT trunc(SYSDATE, 'iw') FROM dual union all SELECT trunc(SYSDATE+1, 'iw') FROM dual union all SELECT trunc(SYSDATE+2, 'iw') FROM dual
SELECT TRUNC(TRUNC(SYSDATE, 'iw')-1, 'iw') FROM dual union all SELECT TRUNC(SYSDATE, 'iw')-7 FROM dual