如何为数据库对象分配唯一的ID

Question

In my app, any user can create a post object which contains a title, description, and ID. These post objects are stored in a database within a server. However, I need a way to assign unique ID's to the posts, so I can assign the user to their post (only the ID of a post will be stored in the core data of the poster's phone). Right now I'm using integers as the ID. For example, when a user submits a post, I have it so the database is queried and I find the ID of the last post submitted and then make the ID of the current post being submitted one more than the ID of the last one. Then the post is uploaded to the database. I feel like this is bad practice because if 2 people coincidentally submit their post at the same time, their respective posts could be given the same ID. So, what I'm asking is how should I assign some sort of ID to an object in the database to guarantee it to be unique? Should I assign it in a php script and then somehow return that ID back to Xcode? Sorry, I'm new to this.

Answer 1

You can simply use an auto increment id for your posts, so the database does that job for you.

CREATE TABLE post(
     id INT NOT NULL AUTO_INCREMENT,
     title VARCHAR(255) NOT NULL,
     description VARCHAR(255),
     PRIMARY KEY (id)
);

Simply check Auto increment example in the mysql documentation

after adding data to the table you can fetch the last id of the inserted post with the last_insert_id command.

so if you use PHP as programming language and you are using mysqli for the database access, you can use mysqli_insert_id to fetch the last id (see the example in the php.net documentation for better understanding)