In MySQL 5, what's the convention for returning an error level and a resultset? -

In MySQL 5, what's the convention for returning an error level and a resultset? -

in mysql 5, stored procedure can homecoming number of output parameters, this:

create procedure `test1`(in in1 varchar(64), in in2, out out1 varchar(64), out out2 int, out out3 int)

in mysql 5, stored procedure can return/print resultset, this:

create procedure `test2` () begin select * `table`; end$$

this nice , flexible. in trying communicate outside world, what's convention using flexibility give notice of results (if any) , errors (if any)?

examples:

do set error messages in our output parameters? set them in resultsets? do print out multiple successive resultsets? or limit ourselves 1 resultset? do set resultset null if there errors? do utilize output paramenter integers errors, 0 beingness error free? do utilize output parameter varchars errors, '' (empty string) meaning error free?

i think makes sense utilize signals returning error if it's supported server (5.5 , up).

mysql