Question

我有一个简单的查询，有4个表的连接。它工作正常，现在我需要在该查询中添加一个连接，但这次表根据该查询中的一个参数而变化;

我的查询如下：

SELECT pat.Id,dgroup.Diagnosis as 'Description', ntest.Testname as 'TestName',
       dgroup.Id as 'ProrityId', subt.TestSubType, **ntest.SubGroupId**
  from pat.tbl_PatientTestRecord pat
          JOIN tbl_Test_DiagnosisGroup InTest on pat.IndividualTestId=InTest.Id
          JOIN tbl_NrlTests nTest ON InTest.TestId=nTest.id
          JOIN tbl_DiagnosisGroup dgroup ON Intest.DGId=dgroup.id
          Left Join 
             **tbl_vary**

tbl_vary 取决于 ntest.subgroupID 。并且tbl_vary可能会出现3个表格。

由于我的SQL有点弱，我将非常感谢为此提供适当的解决方案。

Answer 1

一种可能性是UNION子查询：

SELECT pat.Id,dgroup.Diagnosis as 'Description', ntest.Testname as 'TestName',
       dgroup.Id as 'ProrityId', subt.TestSubType, **ntest.SubGroupId**
  FROM pat.tbl_PatientTestRecord pat
  JOIN tbl_Test_DiagnosisGroup InTest on pat.IndividualTestId=InTest.Id
  JOIN tbl_NrlTests nTest ON InTest.TestId=nTest.id
  JOIN tbl_DiagnosisGroup dgroup ON Intest.DGId=dgroup.id
  LEFT JOIN
       (SELECT v1.SubGroupId, v1.Relevant_Col_1 AS rc1, v1.Relevant_Col_2 AS rc2
          FROM table_variant_1 AS v1
         WHERE v1.SubGroupId = ntest.SubGroupID
        UNION
        SELECT v2.SubGroupId, v2.Alternative_1 AS rc1, v2.Alternative_2 AS rc2
          FROM table_variant_2 AS v2
         WHERE v2.SubGroupId = ntest.SubGroupID
        UNION
        SELECT v3.SubGroupId, v3.Other_Source_1 AS rc1, v3.Other_Source_2 AS rc2
          FROM table_variant_3 AS v3
         WHERE v3.SubGroupId = ntest.SubGroupID
       ) AS u
    ON u.SubGroupId = ntest.SubGroupId

在子查询中没有WHERE子句可能会更好，或者可能有其他方法用UNION查询指定连接...你没有提供关于sub如何有那么多的线索 - 应该构建查询。

SQL中的动态表中的条件连接

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