MariaDB CURSOR
示例一：
简单创建CURSO并打开，关闭操作
DELIMITER //
CREATE PROCEDURE
processorders()
BEGIN
DECLARE
ordernumbers CURSOR FOR
SELECT order_num FROM orders;
END;//
DELIMITER ;
DELIMITER //
CREATE OR REPLACE PROCEDURE
processorders()
BEGIN
-- Declare the
cursor
DECLARE ordernumbers CURSOR FOR
SELECT order_num FROM orders;
-- Open the
cursor
OPEN
ordernumbers;
-- Close the
cursor
CLOSE ordernumbers;
END;//
DELIMITER ;
示例二：
打开CURSOR对象并将值FETCH到指定变量中
DELIMITER //
CREATE OR REPLACE 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;
-- Close the
cursor
CLOSE ordernumbers;
END;//
DELIMITER ;
示例三：
定义CONTINUE
HANDLER并重复FETCH，直到CURSOR结束
DELIMITER //
CREATE OR REPLACE 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;
-- End of loop
UNTIL done END
REPEAT;
-- Close the
cursor
CLOSE ordernumbers;
END;//
DELIMITER ;
示例四：
综合
DELIMITER //
CREATE OR REPLACE 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
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;//
DELIMITER ;
(jlive)[crashcourse]>CALL
processorders();
Query OK, 1 row affected (0.01
sec)
(jlive)[crashcourse]>SELECT *
FROM ordertotals;
+-----------+---------+
| order_num | total
|
+-----------+---------+
|
20005 | 158.86 |
|
20006 | 58.30 |
|
20007 | 1060.00 |
|
20008 | 132.50 |
|
20009 | 40.78 |
|
20009 | 40.78 |
+-----------+---------+
6 rows in set (0.00 sec)
去CALL的时候不会显示任何数据，而是把通过CURSOR
FETCH到的值传入PROCEDURE
ordertotal计算出total值，最后将order_num,total插入新表ordertotals中