游標

第一部分：樣例庫的應用

1）創建游標

CREATE PROCEDURE processorders() BEGINDECLARE ordernumbers CURSORFORSELECT order_num FROM orders; END

由于沒有打開游標，此過程不會把數據檢索出來。
2）使用游標數據

CREATE PROCEDURE processorders() BEGIN -- Declare local variables DECLARE o INT; -- Declare the cursor DECLARE ordernumbers CURSOR FOR SELECT order_num FROM orders; -- Open the cursor OPEN ordernumbers; -- Get order number FETCH ordernumbers INTO o; SELECT O; -- Close the cursor CLOSE ordernumbers; END;

查詢結果：

3）循環檢索數據

CREATE PROCEDURE processorders() BEGIN -- Declare local variables DECLARE done BOOLEAN DEFAULT 0; DECLARE o INT; -- Declare the cursor DECLARE ordernumbers CURSOR FOR SELECT order_num FROM orders; -- Declare continue handler DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET done=1; -- Open the cursor OPEN ordernumbers; -- Loop through all rows REPEAT -- Get order number FETCH ordernumbers INTO o; SELECT o; -- End of loop UNTIL done END REPEAT; -- Close the cursor CLOSE ordernumbers; END; ```查詢結果：4）循環處理數據 ```sql CREATE PROCEDURE processorders() BEGIN -- Declare local variables DECLARE done BOOLEAN DEFAULT 0; DECLARE o INT; DECLARE t DECIMAL(8,2); -- Declare the cursor DECLARE ordernumbers CURSOR FOR SELECT order_num FROM orders; -- Declare continue handler,SQLSTATE '02000' 是一個“未找到”條件 DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET done=1; -- Create a table to store the results CREATE TABLE IF NOT EXISTS ordertotals (order_num INT, total DECIMAL(8,2)); -- Open the cursor OPEN ordernumbers; -- Loop through all rows REPEAT -- Get order number FETCH ordernumbers INTO o; -- Get the total for this order CALL ordertotal(o, 1, t); -- Insert order and total into ordertotals INSERT INTO ordertotals(order_num, total) VALUES(o, t); -- End of loop UNTIL done END REPEAT; -- Close the cursor CLOSE ordernumbers; END;

處理結果：

第二部分：所選課題數據庫的應用

1）查詢語句：

CREATE PROCEDURE `calculateprice`() BEGINDECLARE done BOOLEAN DEFAULT 0; DECLARE o INT;DECLARE t INT;DECLARE remainss CURSORFORSELECT goods_id FROM order_detail;CREATE TABLE IF NOT EXISTS pricetotals(id INT,total INT);OPEN remainss;REPEATFETCH remainss INTO o;CALL pricetotal(o,t);INSERT INTO pricetotals(id,total)VALUES(o,t);UNTIL done END REPEAT;CLOSE remainss; END

以下為創建用來計算price*remains的函數：

CREATE PROCEDURE `pricetotal`(IN `inumber` int,OUT `ptotal` decimal) BEGIN#Routine body goes here...SELECT Sum(total_price)FROM order_detailWHERE goods_id = inumberINTO ptotal; END

查詢結果：

參考文章

與50位技術專家面對面20年技術見證，附贈技術全景圖

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