插入帶有計算列的語句

Question

我創建了以下簡單的DataModel ：

我使用以下insert statements插入值：

1）餐桌產品 ：

INSERT INTO test.products
(ProductName, Price)
VALUES 
("Product A","99,99"),
("Product B","49,95"), 
("Product C","5,95");

2）表格順序 ：

INSERT INTO test.orders
(Customer)
VALUES 
("Customer A"),
("Customer B"), 
("Customer B");

到目前為止，所有這些工作正常。

---

現在，在表Products_per_Order我想通過將Price乘以Quantity來計算最后一列OrderValue 。 因此，我嘗試使用以下兩個選項來引用此處的答案，但仍無法使它們起作用：

注意： “ Price ”列正在根據表Products的idProduct獲取價格。
此功能已起作用。 僅與數量相乘不起作用。

選項1：

INSERT INTO test.products_per_order
(Orders_idOrders, Products_idProducts, Price, Quantity, OrderValue)
VALUES
("1","1",(Select Price from test.products where test.products.idProducts = "1"),"5",(Price * Quantity)),
("1","2",(Select Price from test.products where test.products.idProducts = "2"),"4",(Price * Quantity)),
("2","1",(Select Price from test.products where test.products.idProducts = "1"),"10",(Price * Quantity)),
("3","2",(Select Price from test.products where test.products.idProducts = "2"),"3",(Price * Quantity)),
("3","3",(Select Price from test.products where test.products.idProducts = "3"),"9",(Price * Quantity));

選項2：

INSERT INTO test.products_per_order 
(Orders_idOrders, Products_idProducts, Price, Quantity, OrderValue)
    SELECT m.idOrder, m.idProduct, p.price, m.qty, p.price * m.qty
    FROM (SELECT 1 as idOrder, 1 as idProduct, 5 as qty UNION ALL
          SELECT 1 as idOrder, 2 as idProduct, 4 as qty UNION ALL
          SELECT 2 as idOrder, 1 as idProduct, 10 as qty UNION ALL
          SELECT 3 as idOrder, 2 as idProduct, 3 as qty UNION ALL
          SELECT 3 as idOrder, 3 as idProduct, 9 as qty
         ) m
    LEFT JOIN test.products p on p.idProducts = m.idProduct;

您有解決該問題的想法嗎？

Answer 1

您寫道OrderValue是一個計算列，為什么不讓數據庫為您計算它呢？

使用alter table將OrderValue列更改為生成的列，如下所示：

alter table test.products_per_order 
modify column OrderValue int generated always as (Price * Quantity) stored;

這樣，您根本不需要插入它-您的插入將變成這樣：

INSERT INTO test.products_per_order 
(Orders_idOrders, Products_idProducts, Price, Quantity)
    SELECT m.idOrder, m.idProduct, p.price, m.qty
    FROM (SELECT 1 as idOrder, 1 as idProduct, 5 as qty UNION ALL
          SELECT 1 as idOrder, 2 as idProduct, 4 as qty UNION ALL
          SELECT 2 as idOrder, 1 as idProduct, 10 as qty UNION ALL
          SELECT 3 as idOrder, 2 as idProduct, 3 as qty UNION ALL
          SELECT 3 as idOrder, 3 as idProduct, 9 as qty
         ) m
    LEFT JOIN test.products p on p.idProducts = m.idProduct;

Answer 2

參考以下問題的評論，問題是表Products中的prices需要使用來存儲. 作為小數分隔符代替,

如果將表“ Products的“ INSERT STATEMENT ”修改為：

INSERT INTO test.products
(ProductName, Price)
VALUES 
("Product A","99.99"),
("Product B","49.95"), 
("Product C","5.95");

然后運行選項2中的代碼，一切正常。

INSERT INTO test.products_per_order 
(Orders_idOrders, Products_idProducts, Price, Quantity, OrderValue)
    SELECT m.idOrder, m.idProduct, p.price, m.qty, p.price * m.qty
    FROM (SELECT 1 as idOrder, 1 as idProduct, 5 as qty UNION ALL
          SELECT 1 as idOrder, 2 as idProduct, 4 as qty UNION ALL
          SELECT 2 as idOrder, 1 as idProduct, 10 as qty UNION ALL
          SELECT 3 as idOrder, 2 as idProduct, 3 as qty UNION ALL
          SELECT 3 as idOrder, 3 as idProduct, 9 as qty
         ) m
    LEFT JOIN test.products p on p.idProducts = m.idProduct;