1

我有以下来自 SQL 语句的片段

ROW_NUMBER() OVER (ORDER BY CASE
    WHEN @SortBy = 'column1 ASC' THEN cast(column1 AS sql_variant)
    WHEN @SortBy = 'column2 ASC' THEN cast(column2 AS sql_variant)
    WHEN @SortBy = 'column3 ASC' THEN cast(column3 AS sql_variant)
    WHEN @SortBy = 'column4 ASC' THEN cast(column4 AS sql_variant)
    ELSE NULL
END ASC,
CASE
    WHEN @SortBy = 'column1 DESC' THEN cast(column1 AS sql_variant)
    WHEN @SortBy = 'column2 DESC' THEN cast(column2 AS sql_variant)
    WHEN @SortBy = 'column3 DESC' THEN cast(column3 AS sql_variant)
    WHEN @SortBy = 'column4 DESC' THEN cast(column4 AS sql_variant)
    ELSE NULL
END DESC) AS RowNumber

它有效，但它非常重复，有没有办法使 ASC/DESC 也动态化，所以我不需要重复的CASE语句？

4

2 回答 2

1

您可以执行此操作的一种方法是在不同级别定义列别名，以便您可以引用它两次而无需重复表达式。

SELECT *,
       Row_number() OVER (ORDER BY 
                 CASE WHEN @SortBy LIKE '% ASC' THEN sort_col END ASC, 
                 CASE WHEN @SortBy LIKE '% DESC' THEN sort_col END DESC) AS RowNumber
FROM   YourTable
       CROSS APPLY (SELECT CASE
                             WHEN @SortBy LIKE 'column1 %' THEN Cast(column1 AS SQL_VARIANT)
                             WHEN @SortBy LIKE 'column2 %' THEN Cast(column2 AS SQL_VARIANT)
                             WHEN @SortBy LIKE 'column3 %' THEN Cast(column3 AS SQL_VARIANT)
                             WHEN @SortBy LIKE 'column4 %' THEN Cast(column4 AS SQL_VARIANT)
                           END) C(sort_col)

不过，我会考虑为此使用动态 SQL。这种捕获所有查询将扼杀获得可以使用索引来避免排序的好计划的想法。

于 2012-09-27T14:11:34.910 回答
0

我不确定你是否会认为这更简单。它使用算术运算来获得结果，基于降序行号是总计数减去升序这一事实：

((case when @SortBy like '%DESC' then 1 else -1 end) *
 (case when @SortBy like '%DESC'
       then count(*) over ()
       else 0
  end) -
 (ROW_NUMBER() OVER
      (ORDER BY CASE WHEN @SortBy like 'column1%' THEN cast(column1 AS sql_variant)
                     WHEN @SortBy like 'column2%' THEN cast(column2 AS sql_variant)
                     WHEN @SortBy like 'column3%' THEN cast(column3 AS sql_variant)
                     WHEN @SortBy like 'column4%' THEN cast(column4 AS sql_variant)
                     ELSE NULL
                 END)
 )
)

它确实将列列表限制为一个 case 语句。

于 2012-09-27T14:14:56.023 回答