当unpivot没有检测到不同类型的字段时，我们如何转换select查询的所有字段？

SELECT column1, column2, value
FROM (
    SELECT column1, column2, column3, column4
    FROM your_table
) AS source_table
UNPIVOT (
    value FOR column_name IN (column1, column2, column3, column4)
) AS unpivoted_table;

DECLARE @columns NVARCHAR(MAX), @sql NVARCHAR(MAX);

SELECT @columns = COALESCE(@columns + ', ', '') + QUOTENAME(column_name)
FROM information_schema.columns
WHERE table_name = 'your_table';

SET @sql = N'
SELECT column1, column2, value
FROM (
    SELECT ' + @columns + '
    FROM your_table
) AS source_table
UNPIVOT (
    value FOR column_name IN (' + @columns + ')
) AS unpivoted_table;';

EXEC sp_executesql @sql;