Question

SELECT JobID, MAX(DispoInfo1), MAX(DispoInfo5), MAX(DispoInf10)
    FROM
    (
        SELECT RowID AS JobID, FieldName, FieldValue
        FROM FurtherInfo
        WHERE FieldName IN ('DispoInfo1', 'DispoInfo5', 'DispoInf10')
    ) s
    pivot
    (
      MAX(FieldValue)
      FOR FieldName IN (DispoInfo1, DispoInfo5, DispoInf10)
    ) piv

为什么我们不能执行max（text数据类型值），但是可以在SQL中执行max（nvarchar）？

Answer 1

SELECT JobID, MAX(DispoInfo1), MAX(DispoInfo5), MAX(DispoInf10)
FROM
(
    SELECT RowID AS JobID, FieldName,

CAST（FieldValue AS VARCHAR（MAX））AS FieldValue

    FROM FurtherInfo
    WHERE FieldName IN ('DispoInfo1', 'DispoInfo5', 'DispoInf10')
) s
pivot
(
  MAX(FieldValue)
  FOR FieldName IN (DispoInfo1, DispoInfo5, DispoInf10)
) piv

Answer 2

您可以通过将文本字段转换为varchar（max）/ nvarchar（max）来使用max内的文本字段

MAX (CONVERT (varchar(max), fieldvalue ))

对于“ max”运算符，操作数数据类型“ text”无效

2 个答案: