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我的程序有问题。我尝试从销售表中获取值并使用它们进行查询。程序如下所示：

DROP PROCEDURE IF EXISTS turnover;

DELIMITER $$

CREATE PROCEDURE turnover()
BEGIN
    DECLARE col INT;
    DECLARE q TEXT;
    DECLARE i INT DEFAULT 0;
    DECLARE m TEXT;
    SET col = (SELECT count(DISTINCT article) FROM sales);
    SET q = "SELECT article, ";
    WHILE i < co DO
        SET m = (SELECT DISTINCT month FROM sales LIMIT 1 OFFSET i);
        SET q = q + "SUM(IF(month=" + m + ",value,NULL)) AS " + m;
        IF i < (col - 1) THEN
            SET q = q + ", ";
        END IF;
        SET i = i + 1;
    END WHILE;
    SET q = q + " FROM sales GROUP BY article";
    EXECUTE q;
END$$

DELIMITER ;

CALL turnover();

我收到错误：

错误代码：1292。截断不正确的 DOUBLE 值：',value,NULL)) AS'

我怎样才能让它工作？

谢谢。

4

2 回答 2

1

该col问题已在下文中修复或假设。

CREATE SCHEMA safe_Tuesday_01; -- safe sandbox
USE safe_Tuesday_01;    -- DO the work in this db to test it

-- a fake table, we need something
create table sales 
(   article varchar (100) not null,
    month int not null
);

第 1 步，找出字符串的样子：

DROP PROCEDURE IF EXISTS turnover;
DELIMITER $$
CREATE PROCEDURE turnover()
BEGIN
    DECLARE col INT;
    DECLARE q TEXT;
    DECLARE i INT DEFAULT 0;
    DECLARE m TEXT;
    SET col = (SELECT count(DISTINCT article) FROM sales);
    SET q = "SELECT article, ";
    WHILE i < col DO
        SET m = (SELECT DISTINCT month FROM sales LIMIT 1 OFFSET i);
        SET q = CONCAT(q,"SUM(IF(month=" + m + ",value,NULL)) AS ", m);
        IF i < (col - 1) THEN
            SET q = q + ", ";
        END IF;
        SET i = i + 1;
    END WHILE;
    SET q = CONCAT(q," FROM sales GROUP BY article");
    select q;
    -- EXECUTE q; -- No no no this is wrong anyway
END$$
DELIMITER ;

CALL turnover();

SELECT article, FROM sales GROUP BY article

好吧，上面SELECT看起来并不那么热。在步骤 1 中反复修复您的逻辑以修复该字符串。

第 2 步，当您修复上面的代码时，请在下面插入。请注意，目前，它不是固定的。所以，再一次，在上面。

但是在下面，使用PREPARED STATEMENT你不是的正确的。

DROP PROCEDURE IF EXISTS turnover;
DELIMITER $$
CREATE PROCEDURE turnover()
BEGIN
    DECLARE col INT;
    DECLARE q TEXT;
    DECLARE i INT DEFAULT 0;
    DECLARE m TEXT;
    SET col = (SELECT count(DISTINCT article) FROM sales);
    SET q = "SELECT article, ";
    WHILE i < col DO
        SET m = (SELECT DISTINCT month FROM sales LIMIT 1 OFFSET i);
        SET q = CONCAT(q,"SUM(IF(month=" + m + ",value,NULL)) AS ", m);
        IF i < (col - 1) THEN
            SET q = q + ", ";
        END IF;
        SET i = i + 1;
    END WHILE;
    SET q = CONCAT(q," FROM sales GROUP BY article");
    -- select q;
    SET @theSQL=q;
    PREPARE stmt1 FROM @theSQL;
    EXECUTE stmt1;
    DEALLOCATE PREPARE stmt1;
END$$
DELIMITER ;

完成后，

DROP SCHEMA safe_Tuesday_01; -- clean up, poof, sandbox is gone

CONCAT是你的朋友。你错过了这一步。重要的是PREPARE针对用户变量（带有@符号）而不是本地变量（来自 a DECLARE）工作，否则它会爆炸。所以我用@theSQL

再次，请参阅 MySQL 手册页PREPARE Syntax。正确设置字符串很重要。这就是第 1 步的重点。只有这样，您才能进入第 2 步并使用它。

于 2016-11-23T00:45:28.047 回答
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它发生在SELECT DISTINCT month FROM sales不返回任何东西时。在下一行，查询片段生成为SUM(IF(month=,value,NULL)) AS，当然，那里有一个错误（也许 MySQL 没有产生正确的错误消息，但这就是错误所在）。

错误的原因是与未知变量WHILE进行比较的行。它可能应该是：ico

WHILE i < col DO

但这并不能解决问题，因为col是 的不同值的数量，article并且您从 1 迭代到col的不同值month。很可能它们的数量不同，如果文章数量更大，那么错误将再次发生。

于 2016-11-23T00:26:55.893 回答