在Mysql中创建程序时出错，如何解决？

Question

我正在尝试在 Mysql 中创建一个过程，但在第 12 行出现错误。

它说：

数据库更改查询正常，0 行受影响，1 个警告（0.00 秒）

ERROR 1064 (42000)：您的 SQL 语法有错误；检查 与您的 MySQL 服务器版本相对应的手册 'declare required_date date default 附近使用的语法 cast('0001-01-01' 作为日期); 在第 12 行声明 错误 1305 (42000)：PROCEDURE classicmodels.getInfo 不存在 +---------+ | @结果 | +---------+ |空 | +---------+ 1 行（0.00 秒）

我的代码：

use classicmodels;

delimiter $$
drop procedure if exists `getInfo` $$
create procedure getInfo(in customer_number int(11), in order_number int(11))
begin

    if order_number = 0 and customer_number != 0 THEN
        select orders.orderDate, orders.requiredDate, orders.shippedDate from orders
            inner join customers on customers.customerNumber = orders.customerNumber
            where customers.customerNumber = customer_number;
    elseif order_number != 0 and customer_number = 0 THEN
        select orders.orderDate, orders.requiredDate, orders.shippedDate from orders
            where orders.orderNumber = order_number;
    ELSEIF order_number != 0 and customer_number != 0 THEN
        declare required_date date default cast('0001-01-01' as date);
        declare shipped_date date default cast('9999-01-01' as date);

        select requiredDate into required_date, shippedDate into shippedDate from orders
            inner join customers on customers.customerNumber = orders.customerNumber
            where customers.customerNumber = customer_number and orders.orderNumber = order_number;

        if required_date = shipped_date then 
            select "dap ung tot";
        else
            select "dap ung khong tot";
        end if;
    end if;

end $$
delimiter ;

call getInfo(353,10121);

select @result;


-- C:\Program Files\MySQL\MySQL Server 8.0\bin

Answer 1

我在这里发现了 2 个问题。

1. 您不能在条件语句中声明变量。
2. 由于您的变量是标量，请将结果限制为 1。
3. 你不需要这些变量，你可以用select case代替它，这样你就可以获得多行

这是你的完整脚本。

use classicmodels;

delimiter $$
drop procedure if exists `getInfo` $$
create procedure getInfo(in customer_number int(11), in order_number int(11))
begin


    if order_number = 0 and customer_number != 0 THEN
        select orders.orderDate, orders.requiredDate, orders.shippedDate from orders
            inner join customers on customers.customerNumber = orders.customerNumber
            where customers.customerNumber = customer_number;
    elseif order_number != 0 and customer_number = 0 THEN
        select orders.orderDate, orders.requiredDate, orders.shippedDate from orders
            where orders.orderNumber = order_number;
    elseif order_number != 0 and customer_number != 0 THEN

        select case when required_date = shippedDate then 'dap ung tot' else 'dap ung khong tot' end from orders
            inner join customers on customers.customerNumber = orders.customerNumber
            where customers.customerNumber = customer_number and orders.orderNumber = order_number

    end if;

end $$
delimiter ;

call getInfo(353,10121);

select @result;