Question

每当我尝试使用select语句更新表时，都会从代码中收到预期的错误，尽管我正在尝试不同的解决方法，但没有成功的希望。我的问题的任何帮助将不胜感激。谢谢。

UPDATE `table`
SET Slope = CASE

when (SELECT ((SELECT (SELECT IntColumn FROM `table` ORDER by DateColumn desc limit 1) - (SELECT IntColumn FROM `table` ORDER by DateColumn ASC limit 1) FROM DUAL)) as x) > 0 THEN 'Uptrend' 

when (SELECT ((SELECT (SELECT IntColumn FROM `table` ORDER by DateColumn desc limit 1) - (SELECT IntColumn FROM `table` ORDER by DateColumn ASC limit 1) FROM DUAL)) AS x) < 0 THEN 'Downtrend' 

when (SELECT ((SELECT (SELECT IntColumn FROM `table` ORDER by DateColumn desc limit 1) - (SELECT dialcount FROM `table` ORDER by DateColumn ASC limit 1) FROM DUAL)) AS x) = 0 THEN 'Notrend' 

else 'unknown' END

UPDATE `table`
SET Slope = CASE
when ((SELECT (SELECT IntColumn FROM `table` ORDER by DateColumn desc limit 1) - (SELECT IntColumn FROM `table` ORDER by DateColumn ASC limit 1) FROM DUAL)) > 0 THEN 'Uptrend' 
when ((SELECT (SELECT IntColumn FROM `table` ORDER by DateColumn desc limit 1) - (SELECT IntColumn FROM `table` ORDER by DateColumn ASC limit 1) FROM DUAL)) < 0 THEN 'Downtrend' 
when ((SELECT (SELECT IntColumn FROM `table` ORDER by DateColumn desc limit 1) - (SELECT dialcount FROM `table` ORDER by DateColumn ASC limit 1) FROM DUAL)) = 0 THEN 'Notrend' 

else 'unknown' END

Answer 1

update table set Slope = case 
when ((SELECT IntColumn FROM `table` ORDER by DateColumn desc limit 1) - (SELECT IntColumn FROM `table` ORDER by DateColumn ASC limit 1))>0 then 'Uptrend'
when ((SELECT IntColumn FROM `table` ORDER by DateColumn desc limit 1) - (SELECT IntColumn FROM `table` ORDER by DateColumn ASC limit 1))<0 then 'Downtrend'
when ((SELECT IntColumn FROM `table` ORDER by DateColumn desc limit 1) - (SELECT IntColumn FROM `table` ORDER by DateColumn ASC limit 1))=0 then 'Notrend'
else 'unknown' end

希望有帮助！

Answer 2

我很高兴在经过大量搜索，尝试和错误之后终于可以为我工作，并且我想与希望与case方法一起使用此示例的任何人分享。它如下：

更新table SET斜率=箱 when（（SELECT（SELECT（SELECT intcolumn FROM（SELECT intcolumn FROM table ORDER by DateColumn desc limit 1）as lastdc）-（SELECT intcolumn FROM（SELECT intcolumn FROM table ORDER by DateColumn ASC limit 1） as firstdc）FROM DUAL）as dff））> 0 THEN'上升趋势' when（（SELECT（SELECT（SELECT intcolumn FROM（SELECT intcolumn FROM table ORDER by DateColumn desc limit 1）as lastdc）-（SELECT intcolumn FROM（SELECT intcolumn FROM table ORDER by DateColumn ASC limit 1） as firstdc）FROM DUAL）as dff））<0 THEN'下降趋势' when（（SELECT（SELECT（SELECT intcolumn FROM（SELECT intcolumn FROM table ORDER by DateColumn desc limit 1）as lastdc）-（SELECT intcolumn FROM（SELECT intcolumn FROM table ORDER by DateColumn ASC limit 1） as firstdc）FROM DUAL）as dff））= 0然后'Notrend' 其他“未知” END

Answer 3

如果您只想查询计算斜率，则应执行以下操作：

SELECT CASE WHEN lastInt > firstInt THEN 'Uptrend'
    WHEN lastInt > firstInt THEN 'Downtrend'
    WHEN lastInt > firstInt THEN 'Notrend'
    END AS `slope`
FROM (
    SELECT (SELECT IntColumn FROM `table` ORDER BY DateColumn DESC LIMIT 1) AS lastInt
        , (SELECT IntColumn FROM `table` ORDER BYDateColumn ASC LIMIT 1) AS firstInt
    ) AS boundInts
;

表名指定了两次，既作为更新的目标，又作为单独的数据源

3 个答案: