MySQL遊標

遊標 cursor

相似於迭代器，將查詢結果經過迭代器一一取出

基礎語法

DECLARE [遊標名] CURSOR FOR [查詢語句] ;

越界標識

DECLARE flag INT DEFAULT 1;	
DECLARE CONTINUE|EXIT|UNDO HANDLER FOR NOT FOUND SET flag := 0;

當遊標取值爲空時，會觸發越界標識，將flag置爲0 CONTINUE 後面的語句繼續 EXIT 後面的語句結束 UNDO 前面的語句撤銷

注意：flag變量聲明須要在遊標聲明語句以前，不然會報錯。

使用例子

DELIMITER $;
 CREATE PROCEDURE p11()
 BEGIN
	DECLARE exam_id INT ;
	DECLARE exam_name VARCHAR(20);

	DECLARE flag INT DEFAULT 1;	
	
	DECLARE getRow CURSOR FOR SELECT id, NAME FROM exam ;	
	DECLARE EXIT HANDLER FOR NOT FOUND SET flag := 0;
	
	OPEN getRow;
	
	REPEAT
		FETCH getRow INTO exam_id , exam_name;
		SELECT exam_id , exam_name FROM DUAL;
		 
	UNTIL flag = 0 END REPEAT;
	
	CLOSE getRow;
 END$