如何在mysql中形成一个存储过程，它可以先检查多个表上的多个值，然后如果为真则插入到db中

Question

实际问题陈述如下：

• 产品（prod_id、prod_name、qty_on_hand）

• 订单（cust_id、prod_id、order_date、qty_ordered）

• 客户（cust_id、cust_name、电话、地址）

“编写一个存储过程以将 cust_id、prod_id 和 qty_ordered 作为输入。程序应检查是否可以满足特定客户的订单，如果是，则插入新订单并更新手头的产品数量。如果无法完成订单。Output 参数必须具有 qty_on_hand 的更新值”

我是 plsql 的新手，所以请忽略愚蠢的错误。 我试着编写这样的代码：

delimiter $$
-- creating procedure
CREATE PROCEDURE order_request( cust_id int,  prod_id int, qty_ordered int)
BEGIN

IF( customer.cust_id != cust_id AND product.prod_id != prod_id AND qty_ordered > product.qty_on_hand) THEN 
SELECT 'invalid details' ;

ELSE INSERT INTO `orders` (`cust_id`, `prod_id`, `order_date`, `qty_ordered`) VALUES (cust_id, prod_id, current_date(), qty_ordered)  ;
 END IF ;
END $$

CALL order_request(3,3,2)$$

显示错误： unknown table customer in field list

Answer 1

我已经解决了这个问题。 这是解决方案：

CREATE DATABASE shopping;
USE shopping;

CREATE TABLE product( prod_id INT PRIMARY KEY, prod_name varchar(20), qty_on_hand INT CHECK(qty_on_hand >= 0));
CREATE TABLE customer( cust_id INT PRIMARY KEY, cust_name varchar(20), phone INT, address varchar(20) );

-- product table insertion
INSERT INTO `product` (`prod_id`, `prod_name`, `qty_on_hand`) VALUES ('1', 'mug', '2');
INSERT INTO `product` (`prod_id`, `prod_name`, `qty_on_hand`) VALUES ('2', 'bowl', '15');
INSERT INTO `product` (`prod_id`, `prod_name`, `qty_on_hand`) VALUES ('3', 'plate', '7');
INSERT INTO `product` (`prod_id`, `prod_name`, `qty_on_hand`) VALUES ('4', 'fork', '40');
INSERT INTO `product` (`prod_id`, `prod_name`, `qty_on_hand`) VALUES ('5', 'spoon', '30');

-- customer table insertion
INSERT INTO `customer` (`cust_id`, `cust_name`, `phone`, `address`) VALUES ('1', 'duke', '1212121212', 'pune');
INSERT INTO `customer` (`cust_id`, `cust_name`, `phone`, `address`) VALUES ('2', 'finn', '190120138', 'waterland');
INSERT INTO `customer` (`cust_id`, `cust_name`, `phone`, `address`) VALUES ('3', 'buck', '98989898', 'delhi');
INSERT INTO `customer` (`cust_id`, `cust_name`, `phone`, `address`) VALUES ('4', 'larry', '738197232', 'jaipur');
INSERT INTO `customer` (`cust_id`, `cust_name`, `phone`, `address`) VALUES ('5', 'edna', '184194791', 'mumbai');


CREATE TABLE orders( cust_id INT, prod_id INT, order_date DATE, qty_ordered INT CHECK(qty_ordered > 0) , FOREIGN KEY (cust_id) REFERENCES customer(cust_id), FOREIGN KEY (prod_id) REFERENCES product(prod_id));

-- orders table insertion
INSERT INTO `orders` (`cust_id`, `prod_id`, `order_date`, `qty_ordered`) VALUES ('1', '2', '2022-09-15', '2');


delimiter $$
-- creating procedure
CREATE PROCEDURE order_request( cust_id_param INT,  prod_id_param INT, qty_ordered_param INT)
BEGIN
IF EXISTS (SELECT cust_id,prod_id,qty_on_hand FROM customer,product WHERE cust_id = cust_id_param AND prod_id = prod_id_param AND qty_on_hand  >= qty_ordered_param)
THEN  INSERT INTO `orders` (`cust_id`, `prod_id`, `order_date`, `qty_ordered`) VALUES (cust_id_param, prod_id_param, current_date(), qty_ordered_param);
UPDATE `product` SET product.qty_on_hand = qty_on_hand - qty_ordered_param WHERE prod_id =  prod_id_param ;
ELSE SELECT 'invalid details' ;
END IF ;
END $$
CALL order_request(1,1,2)$$ -- valid
CALL order_request(3,2,14)$$ -- valid
CALL order_request(5,4,4)$$ -- valid
CALL order_request(10,10,2)$$ -- invalid
select * from orders$$
select * from product$$

-- creating the funtion
CREATE FUNCTION order_details (cust_id_param INT, prod_id_param INT ) RETURNS INT
BEGIN
DECLARE ans int;
SELECT SUM(qty_ordered) INTO ans FROM orders WHERE cust_id = cust_id_param AND prod_id = prod_id_param;
RETURN ans;
END$$

-- calling the funtion
SELECT order_details(5,4)$$