在 Pivot 时从字符串转换日期和/或时间时转换失败

Question

我有以下 SQL 查询：

DECLARE @cols AS NVARCHAR(MAX),
        @query AS NVARCHAR(MAX),
        @OID AS NVARCHAR(MAX) = '(105, 106)',
        @startDate DATETIME = DATETIMEFROMPARTS(2017, 11, 01, 17, 0, 0, 0),
        @endDate DATETIME =  DATETIMEFROMPARTS(2017, 11, 25, 17, 0, 0, 0)

SELECT @cols = STUFF((SELECT ',' + QUOTENAME(Point) 
                      FROM Value
                      GROUP BY Point
                      ORDER BY Point
                      FOR XML PATH(''), TYPE).value('.', 'NVARCHAR(MAX)'), 1, 1, '')

SET @query = 'SELECT timestamp,' + @cols + ' from 
         (
            select timestamp, point, valuenumeric
            from value where point in ' + @OID + ' and Timestamp between ' + 
@startDate + ' and ' + @endDate + '
        ) x
        pivot 
        (
            avg(valuenumeric)
            for point in (' + @cols + ')
        ) p '

execute(@query);

但我收到此错误：

消息 241，第 16 级，状态 1，第 16 行
从字符串转换日期和/或时间时转换失败。

Answer 1

问题不在于这些行，而在于动态 sql 部分中的问题，您将datetime 数据类型@startdate 和@enddate 附加到字符串。应该是：

....
Timestamp between ''' + 
CONVERT(NVARCHAR(50), @startDate, 121)+ ''' and ''' + CONVERT(NVARCHAR(50),@endDate, 121) + '''
        ) x
...

您还需要添加更多'，以便将查询正确组合为动态 sql 查询。

---

所以您的完整查询将是：

DECLARE @cols AS NVARCHAR(MAX),
@query  AS NVARCHAR(MAX),
@OID as NVARCHAR(MAX) = '(105, 106)',
@startDate datetime = convert(datetime,'01-11-2017 6:10:00 PM',105),
 @endDate datetime =  convert(datetime,'30-11-2017 6:10:00 PM',105);

select @cols = STUFF((SELECT ',' + QUOTENAME(Point) 
                from Value
                group by Point
                order by Point
        FOR XML PATH(''), TYPE
        ).value('.', 'NVARCHAR(MAX)') 
    ,1,1,'');

set @query = 'SELECT timestamp,' + @cols + ' from 
         (
            select timestamp, point, valuenumeric
            from value where point in ' + @OID + ' and Timestamp between ''' + 
CONVERT(NVARCHAR(50), @startDate, 121)+ ''' and ''' + CONVERT(NVARCHAR(50),@endDate, 121) + '''
        ) x
        pivot 
        (
            avg(valuenumeric)
            for point in (' + @cols + ')
        ) p ';


 execute(@query);

• Demo。

Answer 2

在与string 连接之前，您需要将datetime 显式转换为varchar

您还需要在 datetime 参数周围再附加两个单引号，以将日期用单引号括起来。

为了避免所有这些麻烦，我建议使用参数化 sql。

set @query = 'SELECT timestamp,' + @cols + ' from 
         (
            select timestamp, point, valuenumeric
            from value where point in ' + @OID + ' and Timestamp between  
@startDate and @endDate 
        ) x
        pivot 
        (
            avg(valuenumeric)
            for point in (' + @cols + ')
        ) p '

exec sp_executesql @query,N'@startDate datetime, @endDate Datetime',@startDate,@endDate;