Mega Code Archive
A simple application of a cursor
<![CDATA[
mysql>
mysql>
mysql>
mysql> CREATE TABLE titles (
-> titleID int(11),
-> title varchar(100),
-> subtitle varchar(100),
-> edition tinyint(4),
-> publID int(11),
-> catID int(11),
-> langID int(11),
-> year int(11),
-> isbn varchar(20),
-> comment varchar(255),
-> ts timestamp,
-> authors varchar(255),
-> PRIMARY KEY (titleID)
-> );
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>
mysql>
mysql> INSERT INTO titles VALUES (1,'Linux','Installation',5,1,57,2,2000,NULL,NULL,'2005-02-28 13:34:21','Michael'),
-> (2,'Excel',NULL,NULL,2,3,NULL,2000,NULL,NULL,'2005-02-28 13:34:22','David'),
-> (3,'XML',NULL,NULL,1,2,NULL,1997,NULL,NULL,'2005-02-28 13:34:22','Edwards'),
-> (4,'PHP',NULL,NULL,3,6,NULL,2000,NULL,NULL,'2005-02-28 13:34:22','Tom'),
-> (5,'MySQL','',0,3,34,NULL,2000,'','','2005-02-28 13:34:22','Paul'),
-> (6,'Java',NULL,NULL,4,34,NULL,1999,NULL,NULL,'2005-02-28 13:34:22','Tim');
Query OK, 6 rows affected (0.00 sec)
Records: 6 Duplicates: 0 Warnings: 0
mysql>
mysql>
mysql>
mysql> delimiter $$
mysql>
mysql> CREATE PROCEDURE cursortest(OUT avg_len DOUBLE)
-> BEGIN
-> DECLARE t, subt VARCHAR(100);
-> DECLARE done INT DEFAULT 0;
-> DECLARE n BIGINT DEFAULT 0;
-> DECLARE cnt INT;
-> DECLARE mycursor CURSOR FOR
->
-> SELECT title, subtitle FROM titles;
->
-> DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1;
->
-> SELECT COUNT(*) FROM titles INTO cnt;
-> OPEN mycursor;
-> myloop: LOOP
-> FETCH mycursor INTO t, subt;
-> IF done=1 THEN LEAVE myloop;
-> END IF;
-> SET n = n + CHAR_LENGTH(t);
-> IF NOT ISNULL(subt) THEN
-> SET n = n + CHAR_LENGTH(subt);
-> END IF;
-> END LOOP myloop;
-> SET avg_len = n/cnt;
-> END$$
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> delimiter ;
mysql>
mysql>
mysql> CALL cursortest(@result);
Query OK, 0 rows affected (0.00 sec)
mysql> SELECT @result;
+-------------+
| @result |
+-------------+
| 6.166666666 |
+-------------+
1 row in set (0.00 sec)
mysql>
mysql>
mysql> drop table titles;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>
]]>