日期比较问题。

Question

select decode( requestdate-handledate,0,1 ) from table1

Answer 1

sorry:
 select decode( sign(requestdate-handledate),1,0,1 ) from table1

Answer 2

1* select decode(sign(to_date('2004-01-02','yyyy-mm-dd')-to_date('2004-01-01','yyyy-mm-dd')),1,0,1
SQL> /DECODE(SIGN(TO_DATE('2004-01-02','YYYY-MM-DD')-TO_DATE('2004-01-01','YYYY-MM-DD')),1,0,1)
-----------------------------------------------------------------------------------------
                                                                                        0SQL> ed
Wrote file afiedt.buf
  1* select decode(sign(to_date('2004-01-01','yyyy-mm-dd')-to_date('2004-01-02','yyyy-mm-dd')),1,0,1
SQL> /DECODE(SIGN(TO_DATE('2004-01-01','YYYY-MM-DD')-TO_DATE('2004-01-02','YYYY-MM-DD')),1,0,1)
-----------------------------------------------------------------------------------------
                                                                                        1SQL> ed
Wrote file afiedt.buf
  1* select decode(sign(to_date('2004-01-01','yyyy-mm-dd')-to_date('2004-01-01','yyyy-mm-dd')),1,0,1
SQL> /DECODE(SIGN(TO_DATE('2004-01-01','YYYY-MM-DD')-TO_DATE('2004-01-01','YYYY-MM-DD')),1,0,1)
-----------------------------------------------------------------------------------------
                                                                                        1SQL>

Answer 3

select decode( requestdate-handledate,1,0,1 ) from table1

Answer 4

sign函數的返回值為-1,0,1
decode函數中能識別字符串和數字，但不能識別表達式（結果為真或假），
所以用sign將表達式的結果轉換為數字，就可以使用decode函數來判斷了，
具體做法LGQDUCKY(飘)說的已經很清楚了