Question

只是想知道是否有办法检查表格的列到达最大长度。

通过以下我能够获得表格列的长度

SELECT MAX(CHARACTER_MAXIMUM_LENGTH) AS LEN, COLUMN_NAME
FROM information_schema.columns
WHERE table_name IN ('TableA')
GROUP BY COLUMN_NAME 
ORDER BY LEN DESC

然后我想用数据检查这些列是否达到MAX长度

下面给出了列的最大长度

SELECT MAX(LENGTH(Col1))
FROM TableA

由于无法在WHERE子句中使用聚合函数，它是如何实现的？

由于

Answer 1

您可以使用join将数据整合在一起：

SELECT MaxLen, ActualLen
FROM (SELECT MAX(CHARACTER_MAXIMUM_LENGTH) AS MaxLen, COLUMN_NAME
      FROM information_schema.columns
      WHERE table_name IN ('TableA') AND COLUMN_NAME = 'COL1'
     ) m CROSS JOIN
     (SELECT MAX(LENGTH(Col1)) as ActualLen
      FROM TableA
     ) c;

我不确定你真正想要的是什么。如果您希望行具有最大值：

select a.*
from tablea a
where length(col1) = (SELECT MAX(CHARACTER_MAXIMUM_LENGTH) AS MaxLen
                      FROM information_schema.columns
                      WHERE table_name IN ('TableA') AND COLUMN_NAME = 'COL1'
                     );

检查表列达到最大长度

1 个答案: