Question

我有一个看起来像这样的SQL数据集：

SourceId  SomeContent   
-------------------
1            aaa        
2            bbb       
3            ccc      
4            ddd    



SourceId ConditionType CondidionValue
-------------------------------
1            1            2
1            2           200
2            1            3
2            2           201
3            1            4

我需要选择具有匹配特定键的SourceId，例如（ConditionType = 1和ConditionValue = 2）和（ConditionType = 2和ConditionValue = 200）应该返回sourceId = 1）。具有指定键的查询只能匹配一个SourceId。

我正试图通过这种方式做到这一点：

SELECT SourceId
  FROM ConditionData
  where ConditionType = 2 and ConditionValue = 200      
  and SourceId  in(
SELECT SourceId 
  FROM ConditionData
  where (ConditionType = 1 and ConditionValue = 2))

是否有更优雅的查询来获取它？

Answer 1

您可以使用聚合：

SELECT  SourceId
FROM    ConditionData
WHERE   (ConditionType = 2 and ConditionValue = 200)
    OR  (ConditionType = 1 and ConditionValue = 2)
GROUP BY SourceId
HAVING  COUNT(1) = 2 -- Alternatively: COUNT(1) > 1

Answer 2

我认为您可以为每种条件使用INNER JOIN

SELECT DISTINCT t1.SourceId 
FROM table1 AS t1
INNER JOIN table2 AS condition1 ON t1.SourceId = condition1.SourceId AND condition1.ConditionType = 1 AND condition1.CondidionValue = 2
INNER JOIN table2 AS condition2 ON t1.SourceId = condition2.SourceId AND condition2.ConditionType = 2 AND condition2.CondidionValue = 200

根据特定键选择行

2 个答案: