Question

我正在执行此查询。

select (select FollowersCount from webanalysis.DataTwUser_followers_history where DataTwUserID='80943' and Date <='2015-01-12' order by Date desc limit 1) - (select FollowersCount from webanalysis.DataTwUser_followers_history where DataTwUserID='80943' and Date >='2014-12-12' order by Date  limit 1) as new;

它正在给我＆＃39; 18446744073709551606＆＃39;这是答案，但我想要＆＃39; -9＆＃39;作为答案。

如果我执行查询1 ，

select FollowersCount from webanalysis.DataTwUser_followers_history where DataTwUserID='80943' and Date <='2015-01-12' order by Date desc limit 1;

它会给我＆＃39; 193＆＃39;作为答案。如果执行此查询2

select FollowersCount from webanalysis.DataTwUser_followers_history where DataTwUserID='80943' and Date >='2014-12-12' order by Date  limit 1;

它会给我＆＃39; 202＆＃39;作为答案，所以我想这样做，

193 - 202 = -9。

我哪里错了？需要帮助。

Answer 1

你有无符号整数值，你正在做减法，MySQL将结果绑定到无符号整数......值溢出（下溢）下限，并“换行”。

要解决此问题，请在减法之前将无符号值CAST或CONVERT转换为signed。

SELECT CAST(( val1 ) AS SIGNED) - CAST(( val2 ) AS SIGNED) AS foo

（用您的子查询替换val1和val2，返回无符号整数值）

如果您愿意，可以使用CONVERT功能代替CAST

SELECT CONVERT(( val1 ),SIGNED) - CONVERT(( val2 ),SIGNED) AS foo

mysql没有得到想要的结果

1 个答案: