我是Tableau的新手，希望/期待我可以从DB2导入SQL，以便在最初拉入并编译可视化。我有一个db2连接，然后转到自定义sql，但之后什么都没有加载。代码不是很复杂，但我确实有一些case语句。我尝试执行if语句，但这似乎没有给予我sql的功能。主要问题是，我需要从两个不同的日期提取一个字段，然后只显示这两个日期的不同结果。在Tableau中使用下面的查询是否可行？

SELECT 
    RMD.ISSUE_ID,
    MAX(CASE WHEN AS_OF_DATE = '2021-08-15' THEN CURRENT.ISSUE_TITLE END) AS CURR_ISSUE_TITLE,
    MAX(CASE WHEN AS_OF_DATE = '2021-08-15' THEN CURRENT.MEMBER_IMPACT END) AS CURR_MEMBER_IMPACT,
    MAX(CASE WHEN AS_OF_DATE = '2021-08-08' THEN CURRENT.MEMBER_IMPACT END) AS PREV_MEMBER_IMPACT,
    MAX(CASE WHEN AS_OF_DATE = '2021-08-15' THEN CURRENT.ISM_STATUS END) AS CURR_ISM_STATUS,
    MAX(CASE WHEN AS_OF_DATE = '2021-08-15' THEN CURRENT.ISSUE_OWNER_ORG END) AS CURR_ISSUE_OWNER_ORG,
    MAX(CASE WHEN AS_OF_DATE = '2021-08-15' THEN CURRENT.ISSUE_OWNER END) AS CURR_ISSUE_OWNER,
    MAX(CASE WHEN AS_OF_DATE = '2021-08-15' THEN CURRENT.ISSUE_APPROVER END) AS CURR_ISSUE_APPROVER
FROM LOD.ISM_ISSUE_SUMMARY_HIST_WKY CURRENT INNER JOIN
     LOD.RMD_ISS_REMED_SUMMARY RMD
     ON CURRENT.ISSUE_ID = RMD.ISSUE_ID
WHERE AS_OF_DATE IN ('2021-08-08', '2021-08-15') 
GROUP BY RMD.ISSUE_ID
HAVING MAX(CASE WHEN AS_OF_DATE = '2021-08-08' THEN CURRENT.MEMBER_IMPACT END) <> MAX(CASE WHEN AS_OF_DATE = '2021-08-15' THEN CURRENT.MEMBER_IMPACT END) ;

我试着写这个，但似乎没有做任何事情，因为它只是查询的一部分，或者我不知道如何完成它来完成完整的查询。

IF [As Of Date] = #2021-08-15# THEN [Issue Title] ELSEIF  

 [As Of Date] = #2021-08-15# THEN [Member Impact] ELSEIF

 [As Of Date] = #2021-08-08# THEN [Member Impact] ELSEIF

 [As Of Date] = #2021-08-015# THEN [Ism Status] ELSEIF

 [As Of Date] = #2021-08-015# THEN [Issue Owner Org] ELSEIF

 [As Of Date] = #2021-08-015# THEN [Issue Owner] ELSEIF 

 [As Of Date] = #2021-08-015# THEN [Issue Approver] END

是否可以直接在Tableau中引入我的查询？