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mysql 如何改正？

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Jun 20, 2016 pm 12:48 PM

SELECT (SELECT REPLACE('500x1x10','x','*') AS a)/5000; 这个结果得到0.1，但是实际应该是1，怎么去改正？

回复讨论(解决方案)

字符串形态的表达式是不会被运算的
mysql 并没有类似 eval 的函数，或许你可以自己写一个

对于你的这个例子，可以写作
SELECT substring_index(a,'*',1) * substring_index(substring_index(a,'*',2),'*',-1) * substring_index(substring_index(a,'*',3),'*',-1)
from (select REPLACE('500x1x10','x','*') AS a) t
但不具备普遍意义

如果mysql字段存储500x1x10字符串，但是计算的时候我需要将x替换成*，才可以进行计算。

可以查询出来了用php计算就简单多了

SELECT process.fid,SUM(CASE WHEN (product.box_product_dimensions/5000)>box_shipping_weight THEN product.box_product_dimensions/5000 ELSE box_shipping_weight END ) AS sumweight, (CASE WHEN (product.box_product_dimensions/5000)>box_shipping_weight THEN product.box_product_dimensions/5000 ELSE box_shipping_weight END ) AS weight FROM `process`  LEFT JOIN product ON product.pid=process.pid WHERE 1 AND process.receiver_id>0 AND statu="3" AND property="转仓单" AND isover="N" GROUP BY fid

这是我sql当中其中一段sql，贴出来给你看下。如果计算拿到程序里面，就不是很方便。

product.box_product_dimensions 存储的是字符串，形如：14x12x36 需要计算的话，替换改成14*12*36

你#4的代码与你主贴的问题根本就不是一回事

SELECT process.sku,process.fid,SUM(CASE WHEN (REPLACE(product.box_product_dimensions,'x','*')/5000)>box_shipping_weight THEN product.box_product_dimensions/5000 ELSE box_shipping_weight END ) AS sumweight,
(CASE WHEN (REPLACE(product.box_product_dimensions,'x','*')/5000)>box_shipping_weight THEN product.box_product_dimensions/5000 ELSE box_shipping_weight END ) AS weight FROM `process`
LEFT JOIN product ON product.pid=process.pid WHERE 1 AND process.receiver_id>0 AND statu="3" AND property="转仓单" AND isover="N" GROUP BY fid

product.box_product_dimensions 存储的是字符串，形如：14x12x36

那我#1已经明确的告诉你了，除非你自己写一个函数，否则是不可能指行字符串中的表达式的

SELECT process.sku,process.comment2,SUM(CASE WHEN (SELECT (SELECT SUBSTRING_INDEX(box_product_dimensions,'x',1))*(SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(box_product_dimensions,'x',2),'x',-1))*(SELECT SUBSTRING_INDEX(box_product_dimensions,'x',-1))/5000)>box_shipping_weight THEN (SELECT (SELECT SUBSTRING_INDEX(box_product_dimensions,'x',1))*(SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(box_product_dimensions,'x',2),'x',-1))*(SELECT SUBSTRING_INDEX(box_product_dimensions,'x',-1))/5000)ELSE box_shipping_weight END ) AS sumweight, (CASE WHEN (SELECT (SELECT SUBSTRING_INDEX(box_product_dimensions,'x',1))*(SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(box_product_dimensions,'x',2),'x',-1))*(SELECT SUBSTRING_INDEX(box_product_dimensions,'x',-1))/5000)>box_shipping_weight THEN (SELECT (SELECT SUBSTRING_INDEX(box_product_dimensions,'x',1))*(SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(box_product_dimensions,'x',2),'x',-1))*(SELECT SUBSTRING_INDEX(box_product_dimensions,'x',-1))/5000) ELSE box_shipping_weight END ) AS weight FROM `process`  LEFT JOIN product ON product.pid=process.pid WHERE 1 AND process.receiver_id>0 AND statu="3" AND property="转仓单" AND isover="N"   GROUP BY comment2

( SELECT SUBSTRING_INDEX(box_product_dimensions,'x',1))？？？
为什么要 SELECT ？？

好像是可以不要的，但是这样的话，应该可以实现的。

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