LEFT_JOIN

You must execute the code again to save those values in the database.

-- 客戶表
CREATE TABLE Customers (
    CustomerID INT PRIMARY KEY, -- 客戶編號，主鍵
    CustomerName VARCHAR(100) NOT NULL, -- 客戶姓名
    ContactNumber VARCHAR(20), -- 聯絡電話
    Email VARCHAR(255) -- 電子郵件
);

-- 插入客戶資料
INSERT INTO Customers (CustomerID, CustomerName, ContactNumber, Email) VALUES
(1, 'Stella', '0981-123-456', 'stelladai1028@gmail.com'),
(2, 'Bob', '0982-789-000', 'bob@gmail.com'),
(3, 'Charlie', '0983-666-777', 'charlie@gmail.com'),
(4, 'David', '0984-111-333', 'david@gmail.com'),
(5, 'Emily', '0985-222-444', 'emily@gmail.com');

-- 訂單表
CREATE TABLE Orders (
    OrderID INT PRIMARY KEY, -- 訂單編號，主鍵
    CustomerID INT, -- 客戶編號，外鍵
    OrderDate DATE, -- 訂單日期
    Amount DECIMAL(10, 2), -- 訂單金額
    FOREIGN KEY (CustomerID) REFERENCES Customers(CustomerID) -- 外鍵約束，連接 Customers 表
);

-- 插入訂單資料
INSERT INTO Orders (OrderID, CustomerID, OrderDate, Amount) VALUES
(101, 1, '2023-12-11', 250.00),
(102, 2, '2024-01-22', 300.00),
(103, 3, '2024-02-29', 150.00),
(104, 6, '2024-03-11', 400.00),
(105, 7, '2024-04-22', 100.00);

-- 查詢Left Join資料
SELECT Customers.CustomerID, Customers.CustomerName, Orders.OrderID, Orders.Amount
FROM Customers
LEFT JOIN Orders ON Customers.CustomerID = Orders.CustomerID;

CustomerID	CustomerName	OrderID	Amount
1	Stella	101	250
2	Bob	102	300
3	Charlie	103	150
4	David
5	Emily