数据库|mysql教程
mysql
数据库-mysql教程
本篇文章将介绍存储过程返回多个结果集时是什么结果，希望给大家以参考作用。
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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。
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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(多个结果集)：
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_noAND status = Shipped; -- canceled SELECT count(*) INTO canceled FROM orders WHERE customerNumber = cust_noAND status = Canceled; -- resolved SELECT count(*) INTO resolved FROM orders WHERE customerNumber = cust_noAND status = Resolved; -- disputed SELECT count(*) INTO disputed FROM orders WHERE customerNumber = cust_noAND 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
