如何通过访问多个表中的信息以获得最终结果来解决 sql 问题

Question

你好，我这周正在写一些关于家庭作业的问题，但我被这个问题困住了。我需要在不使用 join

的情况下从多个 table 收集信息

显示每个客户库存请求中请求的每种产品的列表。展示客户名称、产品编号和请求数量，按客户名称排序，然后产品编号。

我当前的代码显示了一个输出，但没有给出正确的结果。它打印 table 的内容 5 次，而不是根据问题打印一次。

SELECT CLIENT.clientName, REQUEST_LIST.productNum, REQUEST_LIST.qtyRequested
FROM CLIENT, REQUEST_LIST 
WHERE CLIENT.clientNum IN (
    SELECT clientNum
    FROM STOCK_REQUEST)
    AND REQUEST_LIST.requestNum IN (
        SELECT requestNum
        FROM STOCK_REQUEST)
ORDER BY CLIENT.clientName , REQUEST_LIST.productNum

这里是 table：

(stock request) 
INSERT INTO Stock_Request (requestDate, clientNum)
    VALUES ('2020-12-10',1);
INSERT INTO Stock_Request (requestDate, clientNum)
    VALUES ('2020-05-04',2);
INSERT INTO Stock_Request (requestDate, clientNum)
    VALUES ('2021-07-06',3);
INSERT INTO Stock_Request (requestDate, clientNum)
    VALUES ('2021-07-08',4);
INSERT INTO Stock_Request (requestDate, clientNum)
    VALUES ('2022-02-07',5);


(request list) 
INSERT INTO Request_List (requestNum, productNum, qtyRequested)
    VALUES (1,1,1);
INSERT INTO Request_List (requestNum, productNum, qtyRequested)
    VALUES (2,2,2);
INSERT INTO Request_List (requestNum, productNum, qtyRequested)
    VALUES (3,3,3);
INSERT INTO Request_List (requestNum, productNum, qtyRequested)
    VALUES (4,4,4);
INSERT INTO Request_List (requestNum, productNum, qtyRequested)
    VALUES (5,5,5);

(client) 
INSERT INTO Client (clientName)
    VALUES ('Mike');
INSERT INTO Client (clientName)
    VALUES ('John');
INSERT INTO Client (clientName)
    VALUES ('Sally');
INSERT INTO Client (clientName)
    VALUES ('Margret');
INSERT INTO Client (clientName)
    VALUES ('Max');

如有任何帮助，我们将不胜感激。

预期输出：（不是实际数字）

client number |   product number | quantity requested

John Smith.        1.                3


Margret Thatcher.    3.                7

Max Payne.          6.                1

Mike Costello.      2.                1

Sally Barbarella.    4.               4

Answer 1

首先，您不需要使用子查询从 stock_request table 中获取 clien_num 和 request_num 值。只需在查询的 where 子句中使用条件即可。行集受 stock_request 条记录限制，行值允许从 client 和 request_list table 中获取适当的值。

其次，我建议你不要使用区分大小写的 table 和列名，它可能会导致拼写错误。

最后，你的查询应该是这样的

SELECT 
    client.client_name, 
    request_list.product_num, 
    request_list.qty_requested
FROM client, request_list, stock_request 
WHERE client.client_num = stock_request.client_num AND stock_request.request_num = request_list.request_num
ORDER BY client.client_name , request_list.product_num

勾选fiddlehttps://www.db-fiddle.com/f/nFQ3s1GGEELCMoPBvPYwyk/1

如何通过访问多个表中的信息以获得最终结果来解决 sql 问题

how to solve sql problem by accessing information from multiple tables to get end result

mysql

sql