如何使用基于其他字段的php增加表中的字段？

Question

I have three fields in the table as follows:

| event_id | email | count |

Now, I have to increment the values in the count field whenever event_id is found same. The increment has to be done based on the previous count value at the same event_id.

`$sql=$con->query("INSERT INTO usersregisteredevents (event_id,email) VALUES ('$event_id','$email')");`

Please help with this.

Answer 1

1. Select count for the current event_id : SELECT COUNT(count) FROM usersregisteredevents WHERE event_id = "$event_id")
2. Do your insert with the value returned above as "count" value : INSERT INTO usersregisteredevents (event_id, email, count) VALUES ('$event_id', '$email', $count)

Edit :

If you want to start the counter at 1, just write SELECT COUNT(count) + 1 FROM [...]