如果行不存在，则插入而不是更新

Question

UPDATE userpostratings SET rating = $rating WHERE postID = 8

如果在postpostratings中没有一行，postID = 8，我想改为INSERT。这可以用sql完成，还是我应该在php

中完成

由于

托梅克

Answer 1

见这里：How do I update if exists, insert if not (AKA "upsert" or "merge") in MySQL?

Answer 2

如果你在postID上有一个UNIQUE索引，那么你可以这样做：

INSERT INTO userpostratings (rating, postID) VALUES ($rating, 8)
    ON DUPLICATE KEY UPDATE rating = $rating;

Answer 3

你去吧

http://nl2.php.net/manual/en/function.mysql-affected-rows.php

> mysql_query("UPDATE mytable SET used=1
> WHERE id < 10"); printf ("Updated
> records: %d\n",
> mysql_affected_rows());