MySQL存储过程 小问题

下面是我写的一段MYSQL的  问题存储过程：
SQL code:
CREATE PROCEDURE BuyBook(
Cuid int,
Cbid int,OUT Info varchar(50))
BEGIN
DECLARE Cprice float;
DECLARE Cmoney float;
SELECT Cprice = price from Book_Info WHERE bid = Cbid;
SELECT SET Cmoney = money from User_Info WHERE uid = Cuid;
IF(Cmoney < Cprice)
THEN
SET Info = '你没有足够的金额购买此书!';
END IF;
IF(Cmoney > Cprice)
THEN
UPDATE User_Info SET money = money - Cmoney WHERE uid = Cuid;
UPDATE Book_Info SET count = count - 1;
SET Info = '购买成功!';
END IF;
END;

高手帮我看看要怎么改~！
还有·····现在是创建语句 那么修改语句是用ALTER来替换CREATE吗？

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ALTER~修改

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你要怎么改？

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SELECT SET Cmoney = money from User_Info WHERE uid = Cuid
->多了个set吧。

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我写的这段存储过程是错误的，但不知道怎么改正····

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引用

SELECT SET Cmoney = money from User_Info WHERE uid = Cuid
->多了个set吧。

这的确是一个错误，改了以后·····：

[SQL] ALTER PROCEDURE BuyBook(
Cuid int,
Cbid int,
OUT Info varchar(50))
BEGIN
DECLARE Cprice float;
[Err] 1064 - You have an error in your SQL s