Question

据我所知，我可以按照以下的sql查询部分的顺序使用变量：

order by 
case when @var1 = 'priority' then priority end desc,
case when @var2 = 'report_date' then report_date end asc

但是我如何在asc和desc部分使用变量呢？

Answer 1

没有Dynamic SQL每个选项它的子句例如：

ORDER BY
  case when @var1 = 'priority asc' THEN priority END ASC ,
  case when @var1 = 'priority desc' then priority end DESC,
  case when @var2 = 'report_date asc' then report_date end ASC,
  case when @var2 = 'report_date desc' then report_date end DESC

Answer 2

假设您的变量@var3存储了'ASC'或'DESC'个关键字，您可以这样写：

order by 
case when @var1 = 'priority' and @var3 = 'DESC' then priority end DESC,
case when @var1 = 'priority' and @var3 = 'ASC' then priority  end ASC,
case when @var2 = 'report_date' and @var3 = 'ASC' then report_date end ASC,
case when @var2 = 'report_date' and @var3 = 'DESC' then report_date end DESC

Answer 3

您可以通过向Order by引入multiplier hack来动态地对多种类型进行排序。实现将取决于您能够将每个可排序字段转换为整数字段，如下所示：

DECLARE @Var1 NVARCHAR(20);
DECLARE @Var2 NVARCHAR(3);
DECLARE @OrderHack INT;

SET @Var1 = 'priority';
SET @Var2 = 'DESC';

IF (@Var2 = 'ASC')
    SET @OrderHack = 1;
ELSE
    SET @OrderHack = -1;

SELECT * 
    FROM SortTable
    ORDER BY 
        CASE @var1
            WHEN 'priority'
                THEN CONVERT(INT, [priority]) * @OrderHack
            WHEN 'report_date'
                THEN CONVERT(INT, report_date) * @OrderHack
        END;

SqlFiddle here

修改

只是澄清一下，根据@t-clausen.dk的观点，黑客依赖于转换回代表订单的递增数字类型。例如如果您需要DATETIME更高的分辨率以确保排序中也考虑时间组件，则INT @OrderHack可以替换为FLOAT或DECIMAL等。：使用此技术对*CHAR列进行排序可能具有挑战性，尤其是在考虑了大小写和重音敏感度的情况下。

Answer 4

试试这个 -

DECLARE 
      @column VARCHAR(15) = 'object_id'
    , @order CHAR(4) = 'DESC'

DECLARE @SQL NVARCHAR(MAX)
SELECT @SQL = '
SELECT * 
FROM sys.objects 
ORDER BY ' + @column + ' ' + @order

PRINT @SQL
EXEC sys.sp_executesql @SQL

按顺序使用asc和desc的变量

4 个答案: