Question

I’m trying to implement a 3 table item tagging system

Table: Item
Columns: ItemID (primary, auto_increment), Title, Content

Table: Tag
Columns: TagID (primary, auto_increment), Title, TagCount

Table: ItemTag
Columns: ItemID, TagID

Each Title of a tag is unique.
I would like to implement an efficient way of inserting to the Tag table:
1. Check if Title exists
2. If it exists, update TagCount+1
3. Else if it doesn’t exist, insert

I looked into INSERT ON DUPLICATE KEY UPDATE, but I’m confused if it can be applied because my key is the TagID and not the Title.

Answer 1

I’m assuming you are trying to do the insert into the table “Tag”.

You need to modify the table and add a unique index on the title field :

alter table tag add unique index title(title);

Then, you can do the following

insert into tag (Title, TagCount) values ('blah',1)
on duplicate key update TagCount = TagCount + 1;

Hopefully that does the trick for you.