In a previous post, I discussed debugging stored procedures with RESIGNAL, which is of great value when troubleshooting errors raised by your stored procedures, functions, triggers, and events as of MySQL/MariaDB 5.5.
However, as of MySQL 5.6 and MariaDB 10.0, there is GET DIAGNOSTICS, which can be used to get the exact error details as well.
RESIGNAL just outputs the error, as it comes from the server, for instance:
ERROR 1146 (42S02): Table 'db1.t1' doesn't exist
In a previous post, I discussed debugging stored procedures with RESIGNAL, which is of great value when troubleshooting errors raised by your stored procedures, functions, triggers, and events as of MySQL/MariaDB 5.5.
However, as of MySQL 5.6 and MariaDB 10.0, there is GET DIAGNOSTICS, which can be used to get the exact error details as well.
RESIGNAL just outputs the error, as it comes from the server, for instance:
ERROR 1146 (42S02): Table 'db1.t1' doesn't exist
You may not want the error just written to the console, or perhaps you want to at least control how it is written.
It’s common to see exit handler code in the following form:
DECLARE EXIT HANDLER FOR SQLEXCEPTION BEGIN SELECT ...; END;
Where the SELECT outputs something not very useful in many cases.
With GET DIAGNOSTICS, you can get all of the …
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When connecting to MySQL, or executing a query, proper error
handling is required. Many take this very seriously, and do a
construct like mysql_connect() or die() or the
equivalent with mysql_query(). For web apps this
generally makes error codes end up on the user page, you can
easily see this by doing a Google search for some of the common
error texts. Slightly improved apps are nicer to the user and log
the error separately.
But both approaches fail, fundamentally, as they don't take into
account that not all errors are the same and, most importantly,
many error are not fatal but require other forms of action. So
let's look at that, look at what causes the errors so you truly
understand that it's not fatal stuff, and how you can handle
them.
When you get a "not successful" response back from a MySQL API
function, you first need find out what the error is with
mysql_errno() (and …