MySQL 外键和查询

Question

当我需要来自多个不同表的信息时，我试图了解查询数据的细节。

现在我有下表。

CREATE TABLE `orders` (
  `orderNumber` int(11) NOT NULL,
  `orderDate` date NOT NULL,
  `requiredDate` date NOT NULL,
  `shippedDate` date DEFAULT NULL,
  `status` varchar(15) NOT NULL,
  `comments` text,
  `customerNumber` int(11) NOT NULL,
  PRIMARY KEY (`orderNumber`),
  KEY `customerNumber` (`customerNumber`),
  CONSTRAINT `orders_ibfk_1` FOREIGN KEY (`customerNumber`) REFERENCES `customers` (`customerNumber`)
)

CREATE TABLE `orderdetails` (
  `orderNumber` int(11) NOT NULL,
  `productCode` varchar(15) NOT NULL,
  `quantityOrdered` int(11) NOT NULL,
  `priceEach` double NOT NULL,
  `orderLineNumber` smallint(6) NOT NULL,
  PRIMARY KEY (`orderNumber`,`productCode`),
  KEY `productCode` (`productCode`),
  CONSTRAINT `orderdetails_ibfk_2` FOREIGN KEY (`productCode`) REFERENCES `products` (`productCode`),
  CONSTRAINT `orderdetails_ibfk_1` FOREIGN KEY (`orderNumber`) REFERENCES `orders` (`orderNumber`)
)

CREATE TABLE `products` (
  `productCode` varchar(15) NOT NULL,
  `productName` varchar(70) NOT NULL,
  `productLine` varchar(50) NOT NULL,
  `productScale` varchar(10) NOT NULL,
  `productVendor` varchar(50) NOT NULL,
  `productDescription` text NOT NULL,
  `quantityInStock` smallint(6) NOT NULL,
  `buyPrice` double NOT NULL,
  `MSRP` double NOT NULL,
  PRIMARY KEY (`productCode`),
  KEY `productLine` (`productLine`),
  CONSTRAINT `products_ibfk_1` FOREIGN KEY (`productLine`) REFERENCES `productlines` (`productLine`)
)
CREATE TABLE `customers` (
  `customerNumber` int(11) NOT NULL,
  `customerName` varchar(50) NOT NULL,
  `contactLastName` varchar(50) NOT NULL,
  `contactFirstName` varchar(50) NOT NULL,
  `phone` varchar(50) NOT NULL,
  `addressLine1` varchar(50) NOT NULL,
  `addressLine2` varchar(50) DEFAULT NULL,
  `city` varchar(50) NOT NULL,
  `state` varchar(50) DEFAULT NULL,
  `postalCode` varchar(15) DEFAULT NULL,
  `country` varchar(50) NOT NULL,
  `salesRepEmployeeNumber` int(11) DEFAULT NULL,
  `creditLimit` double DEFAULT NULL,
  PRIMARY KEY (`customerNumber`),
  KEY `salesRepEmployeeNumber` (`salesRepEmployeeNumber`),
  CONSTRAINT `customers_ibfk_1` FOREIGN KEY (`salesRepEmployeeNumber`) REFERENCES `employees` (`employeeNumber`)
)

我想要弄清楚的是如何编写一个查询来查找在两个特定日期之间订购的产品的名称。

我一直在查看文档和示例，但我似乎无法理解它。感谢您的帮助。

Answer 1

您需要使用 JOIN 关键字来连接查询的表:

/* Get product names ordered between two dates */
select distinct p.productName
from orders o
inner join orderdetails od on od.orderNumber = o.orderNumber
inner join products p on p.productCode = oi.productCode
where o.orderDate >= @startDate AND o.orderDate < @endDate