Mysql database defines cursor in trigger

The way to define local variables in a database stored procedure must be defined at the beginning of the stored procedure , Then the cursor is a keyword DECLARE Statement , So the essence is still a local variable , Can only be defined at the beginning , So when defining a cursor ,my_cur Can only be defined at the beginning , Can no longer IF Define use after condition .

The conclusion is ： trigger / Define local variables in stored procedures / Trigger can only be at the beginning
in addition ：IF The function body after the condition cannot be empty

DELIMITER //
CREATE TRIGGER before_delete
BEFORE DELETE ON manages 
FOR EACH ROW
BEGIN
DECLARE tar_ID CHAR ( 12 ) ;
DECLARE my_cur CURSOR 
FOR
	SELECT ch
	FROM test 
	WHERE test.ch="a";
	IF tar_ID=OLD.manage_ID THEN
		OPEN my_cur;
		#  Use cursors 
		FETCH my_cur INTO tar_ID;
		close my_cur;
	END IF;
END 


DROP TRIGGER before_insert;