如果id存在，则更新；否则，插入（ODBC）

Question

I'm using a PHP script to connect to a microsoft access database using ODBC

The table I'm working on has an 'id' column. I'd like to INSERT new records if the SKU doesn't already exist, else if the SKU does exist, simply UPDATE that record.

What is the correct SQL for this? Is it possible to do it in one query?

Answer 1

I would rather do it in 2 queries.

For me update or insert they are different BUSINESS logics. To get your code clear and clean it's better you explicitly define the logic for INSERT and UPDATE.

And technically I don't see a Clean way doing it in one SQL statement. Each of statement has to start with a "verb" it's either "UPDATE" or "SELECT" or "DELETE" or something else. Or if you insist to do so, you can try delete the potential existing one before you are doing "insert", then you do the "insert" anyway, but then maybe you get a inconsistent Id for same entity, which could cause problems too.

Or if "id" is primary key, another silly way is to do an "update" anyway, then do "insert" anyway. If there's no valid id, update will fail, and insert will succeed. If there's valid id, update will succeed and insert will fail. You'll get it done without the BUSINESS if-else logic, but everytime there'll be a SQL failure, which IS silly and ugly.

That's pretty much what I can think of.

Answer 2

Personally, I would leave that to the application logic rather than the database logic. You can simply do:

if($id)
{
    $sql = 'UPDATE ... WHERE id = ?'; // assuming use of parameterized query
}
else
{
    $sql = 'INSERT INTO ...';
}

Answer 3

I wouldn't suggest doing it in one query. Check if the value you want to add exists before you do the query to add a new value.