格式化日期校验

create or replace function check_format_date(i_format_date varchar2)
  return number is
  -- =======================================
  --模块名称: 格式化日期校验
  --模块编号:
  --模块描述：日期格式 yyyy-MM-dd, 0-false, 1-true
  -- =======================================
  v_year   char(4);
  v_month  char(2);
  v_date   char(2);
  v_return number(1) default 1;

begin
  if length(i_format_date) > 0 then
    begin
      if TO_NUMBER(i_format_date) > 0 then
        if length(i_format_date) = 8 then
          v_year  := '19' || substrb(i_format_date, 7, 2);
          v_month := substrb(i_format_date, 9, 2);
          v_date  := substrb(i_format_date, 11, 2);
        
          if v_month in ('01', '03', '05', '07', '08', '10', '12') and
             to_number(v_date) between 1 and 31 then
            v_return := 1;
          elsif v_month in ('04', '06', '09', '11') and
                to_number(v_date) between 1 and 30 then
            v_return := 1;
          elsif v_month in ('02') and
                (to_number(v_date) between 1 and 28 or
                ((mod(v_year, 400) = 0 or
                (mod(v_year, 4) = 0 and mod(v_year, 100) <> 0)) and
                to_number(v_date) between 1 and 29)) then
            v_return := 1;
          else
            v_return := 0;
          end if;
        else
          v_return := 0;
        end if;
      
      else
        v_return := 0;
      end if;
    exception
      when others then
        v_return := 0;
    end;
  
  else
    v_return := 0;
  end if;

  return v_return;
end;