深入學習mysql存儲過程

這裏的存儲過程都是通過sql語句實現的，用來練習的表結構：

CREATE TABLE `test` (
  `id` varchar(10) NOT NULL,
  `name` varchar(50) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

代碼一、基本結構

DROP PROCEDURE IF EXISTS test;#如存在同名存儲過程則刪除
CREATE PROCEDURE test()
BEGIN#開始標識
	declare _count int DEFAULT 0;
	#聲明變量，建議變量名可用下劃線開頭不容易出錯
	SELECT count(1) INTO _count FROM test;
	#查找數據並存入變量
	SELECT _count;#輸出變量
END#結束標識

代碼二：循環讀取數據

DROP PROCEDURE IF EXISTS test;#dsad 
CREATE PROCEDURE test()
BEGIN
	declare done int default false;
	declare _id VARCHAR(10);
	declare _name VARCHAR(50);
	declare _cur cursor for (SELECT * FROM test);
	#聲明遊標變量
	declare continue HANDLER for not found set done = true;
	#更新退出循環條件
	open _cur;#打開遊標
	loop1:loop#開始循環
	fetch _cur into _id,_name;#賦值
	if done then  #退出
	leave loop1; 
	end if;
	SELECT _id,_name;
	end loop loop1;
END

代碼三：新增數據

DROP PROCEDURE IF EXISTS test;
CREATE PROCEDURE test(IN _id VARCHAR(10),IN _name VARCHAR(50))
BEGIN
	declare _count int DEFAULT 0;
	SELECT count(1) into _count FROM test WHERE ID = _id;
	IF _count <> 0 then
		SELECT "該ID已存在";
	ELSE 
		INSERT INTO test VALUES(_id,_name);
		COMMIT;
	END IF;

END

代碼四：存儲過程之間的調用（代碼三的改編）

DROP PROCEDURE IF EXISTS _save; 
CREATE PROCEDURE _save(IN _id VARCHAR(10),IN _name VARCHAR(50))
BEGIN
		INSERT INTO test VALUES(_id,_name);
		COMMIT;
END



DROP PROCEDURE IF EXISTS test;
CREATE PROCEDURE test(IN _id VARCHAR(10),IN _name VARCHAR(50))
BEGIN
	declare _count int DEFAULT 0;
	SELECT count(1) into _count FROM test WHERE ID = _id;
	IF _count <> 0 then
		SELECT "該ID已存在";
	ELSE 
		CALL _save(_id,_name);
	END IF;

END