select to_char(trunc(add_months(sysdate,-1),'y'),'yyyy-mm') from dual
SELECT To_Char(Trunc(Add_Months(To_Date('2011-01-12','yyyy-mm-dd'),-1),'yyyy'),'yyyy-mm') FROM dual;
select to_char(trunc(sysdate,'y'),'yyyy-mm') from dual
select trunc(add_months(sysdate,-1),'yyyy') from dual;
sys@SZTYORA> alter session set nls_date_format='yyyy-mm-dd hh24:mi:ss';会话已更改。sys@SZTYORA> select trunc(add_months(sysdate,-1),'yyyy') from dual;TRUNC(ADD_MONTHS(SY ------------------- 2011-01-01 00:00:00
SELECT To_Char(Trunc(Add_Months(To_Date('2011-01-12','yyyy-mm-dd'),-1),'yyyy'),'yyyy-mm') FROM dual;
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2011-01-01 00:00:00