PHP：防止Mysql中的重复标记

I have MySql Table For Tags Like This:

| id |   name    |
| 1  |   Linux   |
| 2  |  Windows  |
| 3  |   Unix    |
| 4  |    Dos    |
| 5  |  FreeBSD  |

In News Page User add New Tags Like This:

Linux,OpenBSD,Test 

Now, Linux Previously added, So I need To add ONLY OpenBSD and Test Into Tags Table. My Mean Is: how to INSERT tags if User tags is New?!

1. Put a UNIQUE constraint on the name column.

2. Use INSERT IGNORE so that inserting a column where name already exists simply skips that row. eg:

   INSERT IGNORE INTO tags (name) VALUES ('Linux'), ('OpenBSD'), ('Test');
   

3. Because you have different casings in your data [eg: linux vs Linux] you either need to make sure that you are using a case-insensitive coallation in your database like utf8_latin1_ci [ci stands for case-insensitive] or be sure to use strtolower() on your data prior to inserting it.

Like Jay suggested, normalise the data, then make the column UNIQUE, and use something like INSERT IGNORE INTO yourTags(name) VALUES(?),(?),(?) (and send in the three values as parameters). I'm also assuming that the ID column is AUTO INCREMENT.