在SQL server 中DATEDIFF函数,在Oracle中用下面的在oracle里建立个函数转化下

create or replace function
-- -- works in roughly the same way as sybase datsdiff
-- call would be eg. datediff( 'month ',date1,date2)
-- p_what would be 'HOUR ', 'DAY ', 'MONTH ' OR 'QUARTER '
datediff( p_what in varchar2,
p_d1 in date,
p_d2 in date ) return number
as
l_result number;
begin
l_result:=null;
if (upper(p_what) = 'MINUTE') then
l_result:=((p_d2-p_d1)*24*60);
end if;
if (upper(p_what) = 'HOUR') then
l_result:=((p_d2-p_d1)*24);
end if;
if (upper(p_what) = 'DAY') then
l_result:=(p_d2-p_d1);
end if;
if (upper(p_what) = 'MONTH') then
l_result:=round(MONTHS_BETWEEN(p_d2,p_d1),0);
end if;
if (upper(p_what) = 'QUARTER') then
l_result:=((floor(MONTHS_BETWEEN(p_d2,TRUNC(p_d2, 'YEAR '))/3)+1) - (floor(MONTHS_BETWEEN(p_d1,TRUNC(p_d1, 'YEAR '))/3)+1) + (((to_char(p_d2, 'yyyy ')) - (to_char(p_d1, 'yyyy ')))*4));
end if;
l_result:=floor(l_result);
return l_result;
end;

SQL> SELECT DATEDIFF( 'MONTH', '11-JUL-1975 ', '07-JUN-2004 ') FROM DUAL;

DATEDIFF( 'MONTH', '11-JUL-1975 ', '07-JUN-2004 ')