PHP：防止Mysql中的重复标记

Question

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?!

Answer 1

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.