MySQL 程序错误 "Truncated incorrect DOUBLE value"

Question

我的程序有问题。我尝试从 sales table 中获取值并使用它们进行查询。过程如下所示：

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 '

我怎样才能让它发挥作用？

谢谢。

Answer 1

当 SELECT DISTINCT month FROM sales 没有 return 任何东西时就会发生这种情况。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 不会产生正确的错误消息，但这就是错误所在） .

错误的原因是 WHILE 行将 i 与未知变量 co 进行比较。它可能应该是：

WHILE i < col DO

但这并没有解决问题，因为 col 是 article 的不同值的数量，并且您在 [=19 的不同值上从 1 迭代到 col =].很可能它们的数量不同，如果文章数量更多，那么错误将再次发生。

Answer 2

col 问题已在下面修复或假定。

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

上面SELECT看起来没那么热。在第 1 步中重复修复您的逻辑以修复该字符串。

第 2 步，当你修改上面的代码时，把下面的代码放进去。请注意，目前它还不是固定的。同样，上面那样做。

但在下文中，使用正确的 PREPARED STATEMENT 而你不是。

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 is your friend. You missed this step. It is important that the PREPARE 适用于用户变量（带有 @ 符号）而不是本地变量（来自 DECLARE），否则它会爆炸。所以我用 @theSQL

修复了上面的问题

再次参见 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。然后您才能继续第 2 步并使用它。

MySQL 程序错误 "Truncated incorrect DOUBLE value"

MySQL error "Truncated incorrect DOUBLE value" in procedure

mysql

sql

mysql-error-1292