Question

我有以下代码 - 这是我第一次尝试使用游标。

DELIMITER $$
DROP PROCEDURE IF EXISTS demo$$
DROP TABLE IF EXISTS temp$$

CREATE TEMPORARY TABLE temp(
    id INTEGER NOT NULL AUTO_INCREMENT,
    start DATETIME NOT NULL,
    end DATETIME NOT NULL,
    PRIMARY KEY(id)
) $$

CREATE PROCEDURE demo()
BEGIN

DECLARE done INT DEFAULT 0;
DECLARE a, b DATETIME;
DECLARE cur1 CURSOR FOR SELECT MAX(end) AS end
FROM    (
        SELECT  id, start,
                end,
                @r := @r + (start > @edate) AS num,
                @edate := GREATEST(@edate, end)
        FROM    (
                SELECT  @r := 0,
                        @edate := '0001-01-01'
                ) vars,
                student_lectures
        WHERE   (
                student_id = 1 AND
                start >= '2010-04-26 00:00:00' AND
                end <= '2010-04-30 23:59:59'
                )
        ORDER BY
                start
        ) q
GROUP BY num;

DECLARE cur2 CURSOR FOR SELECT MIN(start) AS start
FROM    (
        SELECT  id, start,
                end,
                @r := @r + (start > @edate) AS num,
                @edate := GREATEST(@edate, end)
        FROM    (
                SELECT  @r := 0,
                        @edate := '0001-01-01'
                ) vars,
                student_lectures
        WHERE   (
                student_id = 1 AND
                start >= '2010-04-26 00:00:00' AND
                end <= '2010-04-30 23:59:59'
                )
        ORDER BY
                start
        ) q
GROUP BY num
LIMIT 1, 18446744073709551615;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;

OPEN cur1;
OPEN cur2;

    REPEAT
        FETCH cur1 INTO a;
        FETCH cur2 INTO b;
        IF NOT done THEN
            INSERT INTO temp(start, end) VALUES(a,b);
        END IF;
    UNTIL done END REPEAT;

CLOSE cur1;
CLOSE cur2;

END $$

SELECT * FROM temp;

我没有收到任何输出到temp表的内容。运行以下查询给我输出，所以我知道它应该匹配的行 - 但我想我已经犯了一些明显的错误。

SELECT MAX(end) AS end
FROM    (
        SELECT  id, start,
                end,
                @r := @r + (start > @edate) AS num,
                @edate := GREATEST(@edate, end)
        FROM    (
                SELECT  @r := 0,
                        @edate := '0001-01-01'
                ) vars,
                student_lectures
        WHERE   (
                student_id = 1 AND
                start >= '2010-04-26 00:00:00' AND
                end <= '2010-04-30 23:59:59'
                )
        ORDER BY
                start
        ) q
GROUP BY num;

此查询返回的输出：

+---------------------+
| end                 |
+---------------------+
| 2010-04-26 13:00:00 |
| 2010-04-26 18:15:00 |
| 2010-04-27 11:00:00 |
| 2010-04-27 13:00:00 |
| 2010-04-27 18:15:00 |
| 2010-04-28 13:00:00 |
| 2010-04-29 13:00:00 |
| 2010-04-29 18:15:00 |
| 2010-04-30 13:00:00 |
| 2010-04-30 15:15:00 |
| 2010-04-30 17:15:00 |
+---------------------+
11 rows in set (0.02 sec)

Answer 1

您在定义程序后是否正在调用该程序？如：CALL demo();

Answer 2

我不确定，但是你不应该在插入后明确提交吗？

MySQL游标问题

2 个答案: