Question

I am looping through a set of values $id and on certain occasions I need to copy 2 fields of data from one table (product) to another (product_new). Both tables already exist and both contain identical fields ‘product_description’ and ‘image’. I am trying to do this with:

$copy_query = "SELECT product_description, image INTO product_new FROM product WHERE product_id=$id";
$result = mysql_query($copy_query) or die('Could not copy the database data: ' . mysql_error() .  '<br>Query: ' . $copy_query);

The error is ‘Undeclared variable: product_new’. I don’t understand this though because I perform other operations with table product_new without issue. Any thoughts? Thanks.

UPDATE

Thanks for the link to the differences doc. That definitely helped, however I have one more issue. My current query is:

$copy_query = "INSERT INTO product_new (product_description, image)
    SELECT product.product_description, product.image
    FROM product
    WHERE product_id=$id";

but this is writing the data to a new row with product_id = 0. I need it to write to the row with product_id = $id.

Answer 1

MySQL doesn’t support the SELECT INTO syntax.

Also, it’s generally very inefficient to run queries inside of a loop. Instead, you can make a comma separated list of the ids in PHP and use:

$copy_query = '
    INSERT INTO product_new (product_description, image)
    SELECT product_description, image
    FROM   product
    WHERE  product_id IN (' . implode(',', $ids) . ')';

mysql_query($copy_query);

Where $ids is the array of your ids.

This solution needs only to be executed once (rather than many times within a loop).

---

EDIT: If you already have rows that exist in product_new and you want to update them, you can use:

$copy_query = '
    UPDATE product_new a
    JOIN   product b ON a.product_id = b.product_id
                    AND b.product_id IN (' . implode(',', $ids) . ')
    SET    a.product_description = b.product_description,
           a.image = b.image';

mysql_query($copy_query);