mysql一条语句执行有就修改没有就插入的操作

Mysql: Insert or Update in One SQL Statement

Published on Oct 3, 2012 by Jamie Munro

    

I must say, I really wish I knew about this technique years ago – before I started using frameworks to do a lot of my development.  The effort that was wasted in building separate code and separate logic to deal with inserts vs updates, when all of this time, there is a nice and simple feature built-in to Mysql that does this for us…

 The process is quite straight forward, when I run a standard INSERT statement with Mysql, I can provide additional properties for dealing with DUPLICATE KEY, e.g. the record already exists.

Here is an example:

INSERT INTO `table` (`name`, `created`, `modified`)VALUES ('Jamie', NOW(), NOW())ON DUPLICATE KEYUPDATE `name` = 'Jamie', `modified` = NOW()

Notice how in the UPDATE statement I'm only updating the name and modified date.

Another nice example can be used for keeping track of the number of times a tag is used.  Imagine you have a table with a list of tags and their associated count.  You can leverage the above functionality to increase the count each time the tag is used again:

INSERT INTO `tags` (`tag`, `count`, `created`, `modified`)VALUES ('mysql', 1, NOW(), NOW())ON DUPLICATE KEYUPDATE `count` = `count` + 1, `modified` = NOW()

That's it!  No more need to right functionality like:

if ($id == 0) {// do insert} else {// do update}

For my information, visit Mysql Documentation.

原文地址：http://www.endyourif.com/mysql-insert-or-update-in-one-sql-statement/