Mysql 如何使用sql从数据库中的货币中选择零件

请询问我可以使用哪个查询来选择，例如，如果用户的工资为10500，我希望他只能提取10000，而数据库保留剩余余额。我只想让用户在1000

的范围内收款。例如，您可以使用mod函数检查面额是否为1000

MariaDB [sandbox]> select emp_no,salary, salary % 1000 modsalary from employees;
+--------+--------+-----------+
| emp_no | salary | modsalary |
+--------+--------+-----------+
|      1 |  20000 |         0 |
|      2 |  39500 |       500 |
|      3 |  50000 |         0 |
|      4 |  19500 |       500 |
|      5 |  10000 |         0 |
|      6 |  19500 |       500 |
|      7 |  40000 |         0 |
|      9 |   NULL |      NULL |
+--------+--------+-----------+
8 rows in set (0.00 sec)

drop trigger if exists wdl;

delimiter $$ 
CREATE DEFINER=`root`@`localhost` TRIGGER `wdl` before INSERT ON `employees_wdl` FOR EACH 
ROW BEGIN
 declare verr int;
 declare vsalary int;
 set verr = 0;

 if not exists(select 1 from employees where emp_no = new.emp_no) then
     set verr = 1;
 else
    select salary into vsalary from employees  where emp_no = new.emp_no;
    if new.amt > vsalary then set verr = 1; end if;
    if new.amt % 1000 <> 0 then set verr = 1 ; end if;
 end if;
 if verr <> 0 then
    signal sqlstate '45000'
        set message_text = 'Wdl amt incorrect or no employee exists';    
 end if;
END $$
delimiter ;

例如，在触发器中捕获错误

MariaDB [sandbox]> select emp_no,salary, salary % 1000 modsalary from employees;
+--------+--------+-----------+
| emp_no | salary | modsalary |
+--------+--------+-----------+
|      1 |  20000 |         0 |
|      2 |  39500 |       500 |
|      3 |  50000 |         0 |
|      4 |  19500 |       500 |
|      5 |  10000 |         0 |
|      6 |  19500 |       500 |
|      7 |  40000 |         0 |
|      9 |   NULL |      NULL |
+--------+--------+-----------+
8 rows in set (0.00 sec)

drop trigger if exists wdl;

delimiter $$ 
CREATE DEFINER=`root`@`localhost` TRIGGER `wdl` before INSERT ON `employees_wdl` FOR EACH 
ROW BEGIN
 declare verr int;
 declare vsalary int;
 set verr = 0;

 if not exists(select 1 from employees where emp_no = new.emp_no) then
     set verr = 1;
 else
    select salary into vsalary from employees  where emp_no = new.emp_no;
    if new.amt > vsalary then set verr = 1; end if;
    if new.amt % 1000 <> 0 then set verr = 1 ; end if;
 end if;
 if verr <> 0 then
    signal sqlstate '45000'
        set message_text = 'Wdl amt incorrect or no employee exists';    
 end if;
END $$
delimiter ;

---

请告诉我。我根本不明白这一点，我如何在php中应用它请不要，如果这是一个php问题，你应该这样标记。我会在10分钟内删除