[大数据]QianBase-SQL计算当天距生日还有多少天

使用SQL计算当天距生日还有多少天的场景：
一开始使用的SQL写法如下

datediff(DAY,sysdate,to_date(year(sysdate)||substring('1988-07-10',5),'YYYY-MM-DD'))

但后面发现这种写法在遇到闰年的时候存在问题，如下面所示

>>select datediff(DAY,sysdate,to_date(year(sysdate)||substring('1988-07-10',5),'YYYY-MM-DD')) from dual;

(EXPR)     
-----------

        130

--- 1 row(s) selected.
>>select datediff(DAY,sysdate,to_date(year(sysdate)||substring('2020-02-29',5),'YYYY-MM-DD')) from dual;

*** ERROR[8415] The provided DATE, TIME, or TIMESTAMP is not valid and cannot be converted. Source data: 2022-02-29 

--- 0 row(s) selected.

因而换了一种写法，将当前时间的年份修改为生日当年的年份，正确的写法如下：

select datediff(DAY,to_date(substring('2020-02-29',1,4)||substring(to_char(sysdate,'YYYY-MM-DD'),5),'YYYY-MM-DD'),to_date('2020-02-29','YYYY-MM-DD'))from dual;

样例输出为：

>>select datediff(DAY,to_date(substring('2020-02-29',1,4)||substring(to_char(sysdate,'YYYY-MM-DD'),5),'YYYY-MM-DD'),to_date('2020-02-29','YYYY-MM-DD'))from dual;

(EXPR)     
-----------

         -2

--- 1 row(s) selected.
>>select datediff(DAY,to_date(substring('1988-07-10',1,4)||substring(to_char(sysdate,'YYYY-MM-DD'),5),'YYYY-MM-DD'),to_date('1988-07-10','YYYY-MM-DD'))from dual;

(EXPR)     
-----------

        130

--- 1 row(s) selected.