用于 CASE 语句的动态 SQL 以删除硬编码

Question

我有一个需要优化的动态 SQL。我需要使 CASE 表达式动态化。下面列出了 ATTRIBUTE_LIST 和 SCENARIO_LIST。我写了一个函数来动态获取它们。如何替换三个 CASE 表达式并使其动态化？我正在努力避免硬编码。

SET @ATTRIBUTE_LIST = 'symbol_type, currency, performing_status' -- INPUTS
SET @SCENARIO_LIST = 'historicalsimulation_1day_end_10dec2013, historicalsimulation_1day_end_11dec2013'

SELECT CASE
           WHEN (GROUPING(Scenario_Name) = 1) THEN ''ALL''
           WHEN (Scenario_Name = ''[BaseCase]'') THEN ''BaseCase''
           ELSE ISNULL(Scenario_Name, '''')
       END AS Scenario_Name,
       CASE
           WHEN (GROUPING(Symbol_Type) = 1) THEN ''ALL''
           ELSE ISNULL(Symbol_Type, '''')
       END AS Symbol_Type,
       CASE
           WHEN (GROUPING(Currency) = 1) THEN ''ALL''
           ELSE ISNULL(Currency, '''')
       END AS Currency,
       CASE
           WHEN (GROUPING(Performing_Status) = 1) THEN ''ALL''
           ELSE ISNULL(Performing_Status, '''') \
       END AS Performing_Status,
       SUM(Value) AS ScenarioValue
FROM [20151005_171003_UserName_NT-22_Analysis_Tue] o
     LEFT JOIN [20151005_171003_UserName_NT-22_Analysis_Tue_Position_Data] pld 
          ON o.Position_Unique_Identifier=pld.Position_Unique_Identifier
GROUP BY ' + @ATTRIBUTE_LIST + ' WITH CUBE) AS DATA 
   PIVOT ( Sum(scenariovalue)
             FOR scenario_name IN (' + @SCENARIO_LIST + ')'

Answer 1

您似乎正在使用 SQL 服务器。这是一种遍历属性并构建一系列 case 表达式的蛮力方法：

declare @cases nvarchar(max) = '';

declare @l varchar(max) = @ATTRIBUTE_LIST + ',';
declare @ofs int = 0;
declare @pos int = charindex(',', @l, @ofs + 1);

while @pos > 0
begin
    if @cases <> '' set @cases = @cases + ',';
    set @cases = @cases +
            replace('
       CASE WHEN (GROUPING(<COL>) = 1) THEN ''ALL''
           ELSE ISNULL(<COL>, '''')
       END AS <COL>',
           '<COL>', substring(@l, @ofs + 1, @pos - @ofs - 1)
    ); 
    set @ofs = @pos;
    set @pos = charindex(',', @l, @ofs + 1);
end
select @cases;

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