mysql goto,如何在MySQL存储函数中使用goto标签

I would like to use goto in MySQL stored function.

How can I use?

Sample code is:

if (action = 'D') then

if (rowcount > 0) then

DELETE FROM datatable WHERE id = 2;

else

SET p=CONCAT('Can not delete',@b);

goto ret_label;

end if;

end if;

Label: ret_label;

return 0;

解决方案

There are GOTO cases which can't be implemented in MySQL, like jumping backwards in code (and a good thing, too).

But for something like your example where you want to jump out of everything to a final series of statements, you can create a BEGIN / END block surrounding the code to jump out of:

aBlock:BEGIN

if (action = 'D') then

if (rowcount > 0) then

DELETE FROM datatable WHERE id = 2;

else

SET p=CONCAT('Can not delete',@b);

LEAVE aBlock;

end if;

end if;

END aBlock;

return 0;

Since your code is just some nested IFs, the construct is unnecessary in the given code. But it makes more sense for LOOP/WHILE/REPEAT to avoid multiple RETURN statements from inside a loop and to consolidate final processing (a little like TRY / FINALLY).