MySQL Stored Procedure Error Handling

Question

I believe there is nothing currently available in MySQL that allows access to the SQLSTATE of the last executed statement within a MySQL stored procedure. This means that when a generic SQLException is raised within a stored procedure it is hard/impossible to derive the exact nature of the error.

Does anybody have a workaround for deriving the SQLSTATE of an error in a MySQL stored procedure that does not involve declaring a handler for every possible SQLSTATE?

For example - imagine that I am trying to return an error_status that goes beyond the generic "SQLException happened somewhere in this BEGIN....END block" in the following:

DELIMITER $$

CREATE PROCEDURE `myProcedure`(OUT o_error_status varchar(50))
MY_BLOCK: BEGIN

 DECLARE EXIT handler for 1062 set o_error_status := "Duplicate entry in table";
 DECLARE EXIT handler for 1048 set o_error_status := "Trying to populate a non-null column with null value"; 
-- declare handlers ad nauseum here....

 DECLARE EXIT handler for sqlexception set o_error_status:= "Generic SQLException. You'll just have to figure out the SQLSTATE yourself...." ;

-- Procedure logic that might error to follow here...

END MY_BLOCK$$

Any tips?

PS I am running MySQL 5.1.49

Answer 1

I believe there is nothing currently available in MySQL that allows access to the SQLSTATE of the last executed statement within a MySQL stored procedure. This means that ... it is hard/impossible to derive the exact nature of the error.

Luckily that is not true.

SHOW ERRORS LIMIT 1   -- for SQL-state > 2
SHOW WARNINGS LIMIT 1 -- for SQL-state 1,2

Will show the last error or warning.

In order to prevent listing each and every error, you can handle a class of SQL-errors like so:

SQLWARNING is shorthand for the class of SQLSTATE values that begin with '01'.

NOT FOUND is shorthand for the class of SQLSTATE values that begin with '02'. This is relevant only within the context of cursors and is used to control what happens when a cursor reaches the end of a data set. If no more rows are available, a No Data condition occurs with SQLSTATE value 02000. To detect this condition, you can set up a handler for it (or for a NOT FOUND condition). An example is shown in Section 12.7.5, “Cursors”. This condition also occurs for SELECT ... INTO var_list statements that retrieve no rows.

SQLEXCEPTION is shorthand for the class of SQLSTATE values that do not begin with '00', '01', or '02'.

So to handle an exception, you need to only do:

DECLARE EXIT HANDLER FOR SQLSTATE SQLEXCEPTION .....;

Links:
http://dev.mysql.com/doc/refman/5.5/en/signal.html
http://dev.mysql.com/doc/refman/5.0/en/declare-handler.html