Updating an associative table in MySQL - sql

Question

Below is my (simplified) schema (in MySQL ver. 5.0.51b) and my strategy for updating it. There has got to be a better way. Inserting a new item requires 4 trips to the database and editing/updating an item takes up to 7!
items: itemId, itemName
categories: catId, catName
map: mapId*, itemId, catId
* mapId (varchar) is concat of itemId + | + catId
1) If inserting: insert item. Get itemId via MySQL API.
Else updating: just update the item table. We already have the itemId.
2) Conditionally batch insert into categories.
INSERT IGNORE INTO categories (catName)
VALUES ('each'), ('category'), ('name');
3) Select IDs from categories.
SELECT catId FROM categories
WHERE catName = 'each' OR catName = 'category' OR catName = 'name';
4) Conditionally batch insert into map.
INSERT IGNORE INTO map (mapId, itemId, catId)
VALUES ('1|1', 1, 1), ('1|2', 1, 2), ('1|3', 1, 3);
If inserting: we're done. Else updating: continue.
5) It's possible that we no longer associate a category with this item that we did prior to the update. Delete old categories for this itemId.
DELETE FROM MAP WHERE itemId = 2
AND catID <> 2 AND catID <> 3 AND catID <> 5;
6) If we have disassociated ourselves from a category, it's possible that we left it orphaned. We do not want categories with no items. Therefore, if affected rows > 0, kill orphaned categories. I haven't found a way to combine these in MySQL, so this is #6 & #7.
SELECT categories.catId
FROM categories
LEFT JOIN map USING (catId)
GROUP BY categories.catId
HAVING COUNT(map.catId) < 1;
7) Delete IDs found in step 6.
DELETE FROM categories
WHERE catId = 9
AND catId = 10;
Please tell me there's a better way that I'm not seeing.

Answer 1

Also, if you are worried about trips to the db, make steps into a stored procedure. Then you have one trip.

Answer 2

There are a number of things you can do to make a bit easier:
Read about [INSERT...ON DUPLICATE KEY UPDATE][1]
Delete old categories before you insert new categories. This may benefit from an index better.
DELETE FROM map WHERE itemId=2;
You probably don't need map.mapID. Instead, declare a compound primary key over (itemID, catID).
As Peter says in his answer, use MySQL's multi-table delete:
DELETE categories.* FROM categories LEFT JOIN map USING (catId)
WHERE map.catID IS NULL
http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html

Answer 3

Steps 6 & 7 can be combined easily enough:
DELETE categories.*
FROM categories
LEFT JOIN map USING (catId)
WHERE map.catID IS NULL;
Steps 3 & 4 can also be combined:
INSERT IGNORE INTO map (mapId, itemId, catId)
SELECT CONCAT('1|', c.catId), 1, c.catID
FROM categories AS c
WHERE c.catName IN('each','category','name');
Otherwise, your solution is pretty standard, unless you want to use triggers to maintain the map table.