duplicate field value in query.

[Lesiok]

Yours UPDATE query updates ALL record in database and the message shows that there can only be one record for a given number in the database. The WHERE condition is probably missing.

[d_stranz]

And sending a pointer to a local variable as a signal argument is a very bad programming practice. If a slot tries to store that pointer, it will result in a crash later because after the clicked() slot exits, the local variable is gone.

Why don't you simply send the QString itself? You aren't optimizing anything by sending the address of the QString, because the QString implementation will not copy the string until it is modified, so it will not be copied if it is sent as an argument.