mysql存储过程中，IN用来输入参数，OUT用来输出参数，INOUT输入和输出。
IN参数
创建存储过程
mysql> delimiter //
mysql> create procedure proce1(IN count int)
-> begin
-> select count;
-> set count = 2;
-> select count;
-> end
-> //
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执行存储过程
mysql> set @count = 1//
Query OK, 0 rows affected (0.00 sec)
mysql> call proce1(@count)//
+-------+
| count |
+-------+
| 1 |
+-------+
1 row in set (0.00 sec)
+-------+
| count |
+-------+
| 2 |
+-------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
mysql> select @count
-> //
+--------+
| @count |
+--------+
| 1 |
+--------+
1 row in set (0.00 sec)
mysql>
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在上面存储过程中，我们定义了一个参数@count，赋值为1，传入到存储过程中，在存储过程中赋值为2，当存储过程结束后，打印@count的值依旧是1.
OUT参数
创建存储过程
mysql> create procedure proce_out(OUT count int)
-> begin
-> select count;
-> set count = 2;
-> select count;
-> end//
Query OK, 0 rows affected (0.05 sec)
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执行存储过程
mysql> set @count=1;
-> call proce_out(@count);
-> select @count;
-> //
Query OK, 0 rows affected (0.00 sec)
+-------+
| count |
+-------+
| NULL |
+-------+
1 row in set (0.00 sec)
+-------+
| count |
+-------+
| 2 |
+-------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
+--------+
| @count |
+--------+
| 2 |
+--------+
1 row in set (0.00 sec)
mysql>
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@count在外面赋值为1，因为参数是OUT类型，所以存储过程中打印出来为null，存储过程中赋值为2，存储过程结束，查看@count的值，依旧为2。
INOUT 输入输出参数
创建存储过程
mysql> create procedure proce_inout(INOUT count int)
-> begin
-> select count;
-> set count = 2;
-> select count;
-> end;
-> //
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执行存储过程
mysql> set @count = 1;
-> call proce_inout(@count);
-> select @count;
-> //
Query OK, 0 rows affected (0.00 sec)
+-------+
| count |
+-------+
| 1 |
+-------+
1 row in set (0.00 sec)
+-------+
| count |
+-------+
| 2 |
+-------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
+--------+
| @count |
+--------+
| 2 |
+--------+
1 row in set (0.00 sec)
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我们在外面把@count赋值为1，存储过程里面获取到了值，然后赋值为2，存储过程结束后，打印出来的值依旧是2
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版权声明：本文为CSDN博主「徐海兴」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/u012326462/article/details/83445404