MySQL 存储过程返回多值

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 简介：在本教程中，您将学习如何开发返回多个值的存储过程。 MySQL存储函数只返回一个值。要开发返回多个值的存储程序，您需要使用存储过程INOUT或OUT参数。 如果您不熟悉INOUT或OUT参数，请查看存储过程的参数教程以获取详细信息。

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MySQL存储过程返回多个值的实例

我们来看看示例数据库中的orders表。

+----------------+
| orders         |
+----------------+
| orderNumber    |
| orderDate      |
| requiredDate   |
| shippedDate    |
| status         |
| comments       |
| customerNumber |
+----------------+
7 rows in set (0.00 sec)

以下存储过程接受客户编号，并返回发货(shipped)，取消(canceled)，解决(resolved)和争议(disputed)的订单总数。

DELIMITER $$
 
CREATE PROCEDURE get_order_by_cust(
 IN cust_no INT,
 OUT shipped INT,
 OUT canceled INT,
 OUT resolved INT,
 OUT disputed INT)
BEGIN
 -- shipped
 SELECT
            count(*) INTO shipped
        FROM
            orders
        WHERE
            customerNumber = cust_no
                AND status = 'Shipped';
 
 -- canceled
 SELECT
            count(*) INTO canceled
        FROM
            orders
        WHERE
            customerNumber = cust_no
                AND status = 'Canceled';
 
 -- resolved
 SELECT
            count(*) INTO resolved
        FROM
            orders
        WHERE
            customerNumber = cust_no
                AND status = 'Resolved';
 
 -- disputed
 SELECT
            count(*) INTO disputed
        FROM
            orders
        WHERE
            customerNumber = cust_no
                AND status = 'Disputed';
 
END $$

DELIMITER ;

除IN参数外，存储过程还需要四个附加OUT参数：shipped, canceled, resolved 和 disputed。在存储过程中，您使用SELECT带有COUNT函数的语句根据订单的状态获取相应的订单总数，并将其分配给相应的参数。 要使用get_order_by_cust存储过程，请传递客户编号和四个用户定义的变量以获取输出值。 执行存储过程后，使用SELECT语句输出变量值。

CALL get_order_by_cust(141,@shipped,@canceled,@resolved,@disputed);
SELECT @shipped,@canceled,@resolved,@disputed;

+----------+-----------+-----------+-----------+
| @shipped | @canceled | @resolved | @disputed |
+----------+-----------+-----------+-----------+
|       22 |         0 |         1 |         1 |
+----------+-----------+-----------+-----------+
1 row in set (0.00 sec)

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使用PHP调用从返回多个值的存储过程

以下代码段显示如何调用从PHP返回多个值的存储过程。

<?php
/**
 * Call stored procedure that return multiple values
 * @param $customerNumber
 */
function call_sp($customerNumber)
{
    try {
        $pdo = new PDO("mysql:host=localhost;dbname=classicmodels", 'root', '');
 
        // execute the stored procedure
        $sql = 'CALL get_order_by_cust(:no,@shipped,@canceled,@resolved,@disputed)';
        $stmt = $pdo->prepare($sql);
 
        $stmt->bindParam(':no', $customerNumber, PDO::PARAM_INT);
        $stmt->execute();
        $stmt->closeCursor();
 
        // execute the second query to get values from OUT parameter
        $r = $pdo->query("SELECT @shipped,@canceled,@resolved,@disputed")
                  ->fetch(PDO::FETCH_ASSOC);
        if ($r) {
            printf('Shipped: %d, Canceled: %d, Resolved: %d, Disputed: %d',
                $r['@shipped'],
                $r['@canceled'],
                $r['@resolved'],
                $r['@disputed']);
        }
    } catch (PDOException $pe) {
        die("Error occurred:" . $pe->getMessage());
    }
}
 
call_sp(141);

用户定义的变量（以@符号开头）与数据库连接相关联，因此，它们可用于调用之间的访问。 在本教程中，我们向您展示了如何开发一个返回多个值的存储过程以及如何从PHP调用它。

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