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本文实例讲述了mysql存储过程之返回多个值的方法。分享给大家供大家参考，具体如下：

mysql存储函数只返回一个值。要开发返回多个值的存储过程，需要使用带有INOUT或OUT参数的存储过程。咱们先来看一个orders表它的结构：

mysql> desc orders;
+----------------+-------------+------+-----+---------+-------+
| Field     | Type    | Null | Key | Default | Extra |
+----------------+-------------+------+-----+---------+-------+
| orderNumber  | int(11)   | NO  | PRI | NULL  |    |
| orderDate   | date    | NO  |   | NULL  |    |
| requiredDate  | date    | NO  |   | NULL  |    |
| shippedDate  | date    | YES |   | NULL  |    |
| status     | varchar(15) | NO  |   | NULL  |    |
| comments    | text    | YES |   | NULL  |    |
| customerNumber | int(11)   | NO  | MUL | NULL  |    |
+----------------+-------------+------+-----+---------+-------+
7 rows in set

然后嘞，咱们来看一个存储过程，它接受客户编号，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

其实，除IN参数之外，存储过程还需要4个额外的OUT参数：shipped, canceled, resolved 和 disputed。 在存储过程中，使用带有count函数的select语句根据订单状态获取相应的订单总数，并将其分配给相应的参数。按着上面的sql，我们如果要使用get_order_by_cust存储过程，可以传递客户编号和四个用户定义的变量来获取输出值。执行存储过程后，我们再使用SELECT语句输出变量值：

+----------+-----------+-----------+-----------+
| @shipped | @canceled | @resolved | @disputed |
+----------+-----------+-----------+-----------+
|    22 |     0 |     1 |     1 |
+----------+-----------+-----------+-----------+
1 row in set

结合实际应用，我们再来看下从PHP程序中调用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=yiibaidb", 'root', '123456');
    // 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);

上述代码中，在@符号之前的用户定义的变量与数据库连接相关联，因此它们可用于在调用之间进行访问。

好啦，本次分享就到这里了。

更多关于MySQL相关内容感兴趣的读者可查看本站专题：《MySQL存储过程技巧大全》、《MySQL常用函数大汇总》、《MySQL日志操作技巧大全》、《MySQL事务操作技巧汇总》及《MySQL数据库锁相关技巧汇总》

希望本文所述对大家MySQL数据库计有所帮助。