mysql批量更新存储过程怎么写

Question

我要写个存储过程，传入记录数N。
然后查找出按积分排序的前N条记录，然后循环设置记录的排名=i.
请问能给个demo么。

Answer 1

[code="java"]create procedure batchUpdate(in n int)
begin
declare inParam int default n;
declare i int default 1;
declare id int;
declare username varchar(255);
declare integral varchar(255);
declare ranking int;
declare _resultSet cursor for select a.id, a.username,a.integral,a.ranking from user a order by a.integral desc limit inParam;
open _resultSet;
while i <= inParam do
fetch _resultSet into id, username, integral,ranking;
update user a set a.ranking = i where a.id = id;
set i = i +1;
end while;
close _resultSet;
end;

mysql> select * from user;
+----+----------+----------+---------+
| id | username | integral | ranking |
+----+----------+----------+---------+
| 1 | abc | 1 | 0 |
| 2 | abc | 2 | 0 |
| 3 | abc | 3 | 0 |
| 4 | abc | 4 | 0 |
| 5 | abc | 5 | 0 |
| 6 | abc | 6 | 0 |
| 7 | abc | 7 | 0 |
| 8 | abc | 8 | 0 |
| 9 | abc | 9 | 0 |
| 10 | abc | 10 | 0 |
| 11 | abc | 11 | 0 |
| 12 | abc | 12 | 0 |
| 13 | abc | 13 | 0 |
| 14 | abc | 14 | 0 |
+----+----------+----------+---------+
14 rows in set

mysql> call batchUpdate(14);
Query OK, 1 row affected

mysql> select * from user;
+----+----------+----------+---------+
| id | username | integral | ranking |
+----+----------+----------+---------+
| 1 | abc | 1 | 14 |
| 2 | abc | 2 | 13 |
| 3 | abc | 3 | 12 |
| 4 | abc | 4 | 11 |
| 5 | abc | 5 | 10 |
| 6 | abc | 6 | 9 |
| 7 | abc | 7 | 8 |
| 8 | abc | 8 | 7 |
| 9 | abc | 9 | 6 |
| 10 | abc | 10 | 5 |
| 11 | abc | 11 | 4 |
| 12 | abc | 12 | 3 |
| 13 | abc | 13 | 2 |
| 14 | abc | 14 | 1 |
+----+----------+----------+---------+
14 rows in set[/code]