如果存在则更新，如果不存在则插入

可能重复:
如何操作我是否更新(如果存在)，如果不存在，则插入MySQL(又称为upsert或merge)?

Possible Duplicate:
How do I update if exists, insert if not (aka upsert or merge) in MySQL?

我有可以为预订引擎批量更新价格的程序.

I have program that can do batch updating price for booking engine.

用于更新批量价格的示例用户输入是这样的

example user input for to do update batch the price is like this

$dateStart = '2012-12-01';
$dataEnd = '2012-12-31';
$hotelId = 1;
$price = 300000;

数据库就是这样

id | date       | hotelId | price
1  | 2012-12-01 | 1       | 100000

如果date和hotelId已经存在，MySQL查询应该如何进行批处理更新并在有条件的情况下进行插入，然后进行更新，但是如果不存在，则进行插入?

How should the MySQL Query, to do batch update and insert with condition if date and hotelId is already exist then do update, but if not exist do insert?

我知道如果每天进行循环并检查PHP中的数据是否存在，确实会占用大量内存.

I understand if doing looping day by day and checking if data exist or not in PHP will be really spend much memory.

for($i=1; $i<=31; $i++){...}

我正在寻找解决方案，如何使用单个/任何可以节省计算机资源的mysql查询来完成.

I'm looking solution how it can be done with single/any mysql query that can save computer resource.