How to trigger an error in MySQL?

MySQL introduces signals similar to exceptions in other languages. Let's first take a look at the syntax of the signal.

SIGNAL SQLSTATE ' PredefinedValueforSignalError'　
SET MESSAGE_TEXT = 'AnyMessageInformation';

Above, we also set our own error message text.

We will use the above query to obtain the error message with the help of the signal.

mysql > SIGNAL SQLSTATE '42927' SET MESSAGE_TEXT = 'Error Generated';

The following is the output of the above query.

ERROR　1644　(42927): Error Generated

In the above output, “ 42927“is a SQLSTATE,” and “Error Generated” is an error message, we added it.