Question

asset_property table:

| asset_id | property_id | property_value |
|:--------:|:-----------:|:---------------|
| 146      | 1           | 4G             |
| 146      | 3           | 68723-239Gs    |
| 147      | 1           | A7             |

This is my query:

INSERT INTO asset_property (asset_id, property_id, property_value)
VALUES
  (146, 1, '4G'),
  (146, 2, 'Black & Decker'),
  (146, 3, ''),
ON DUPLICATE KEY
UPDATE property_value = VALUES(property_value);

Is there a way to say something like this:

INSERT INTO asset_property (asset_id, property_id, property_value)
VALUES
  (146, 1, '4G'),
  (146, 2, 'Black & Decker'),
  (146, 3, ''),
ON DUPLICATE KEY
UPDATE property_value = VALUES(property_value)
ON VALUES(property_value) IS NULL
DELETE FROM asset_property
WHERE asset_id = VALUES(asset_id)
AND property_id = VALUES(property_id);

Or I could use PHP to determine empty property_value sets and build a second query. So I would need this:

DELETE FROM asset_property
WHERE 'PRIMARY KEY' IN ('146-3');

The syntax is okay, but 0 rows are affected.

I’ve tried this:

SELECT 'PRIMARY KEY' FROM asset_property WHERE asset_id = 146;

But the result is:

| PRIMARY KEY |
|:------------|
| PRIMARY KEY |
| PRIMARY KEY |

The MySQL Manual seams to say you can’t.

Answer 1

DELETE FROM asset_property
WHERE 'PRIMARY KEY' IN ('146-3');

The syntax is okay, but 0 rows are affected.

There aren’t any syntax errors, but that doesn’t mean it’s okay 🙂 @rodrigoap has already explained what that one means, and why 0 rows match.

If you need to delete several records matching a composite primary key, you’re going to have to do one of these:

DELETE FROM asset_property
WHERE (asset_id = 146 AND property_id = 3)
   OR (asset_id = 146 AND property_id = 7)
   OR (asset_id = 146 AND property_id = 18)

or concatenate the fields and test that:

DELETE FROM asset_property
WHERE CONCAT(asset_id, '-', property_id) in ('146-3', '146-7', '146-18')

(this one will be slower, because it can’t take advantage of any indexes)

or just execute multiple delete statements inside of a transaction:

BEGIN
DELETE FROM asset_property
WHERE asset_id = 146 AND property_id = 3
DELETE FROM asset_property
WHERE asset_id = 146 AND property_id = 7
DELETE FROM asset_property
WHERE asset_id = 146 AND property_id = 18
COMMIT