分组和交集的SQL问题

Question

我在MySQL中有此日志表，其中包含ActionName和SourceName列。

可以从不同的来源多次注册相同的动作。

因此，示例表可能看起来像

ActionName    SourceName
----------------------------
Add           S01
Add           S02
Add           S02
Edit          S01
Edit          S01
Delete        S01
Delete        S02

现在，我想查询该表并查找S01和S02都执行的操作。 因此结果将是：

 ActioName
--------------
Add
Delete

如何使用SQL解决此问题？

Answer 1

具体答案...

SELECT
  ActionName
FROM
  yourTable
WHERE
  SourceName in ('S01', 'S02')
GROUP BY
  ActionName
HAVING
  COUNT(DISTINCT SourceName) = 2

针对您的特定问题可能更快...

SELECT
  a.SourceName
FROM
  yourTable  AS a
INNER JOIN
  yourTable  AS b
    ON a.ActionName = b.ActionName
WHERE
      a.SourceName = 'S01'
  AND b.SourceName = 'S02'

一般的答案...

SELECT
  ActionName
FROM
  yourTable
INNER JOIN
  tableWithSourceNames
    ON yourTable.SourceName = tableWithSourceNames.SourceName
GROUP BY
  ActionName
HAVING
  COUNT(DISTINCT yourTable.SourceName) = (SELECT COUNT(DISTINCT SourceName) FROM tableWithSourceNames)

事实证明，这样做的伸缩性非常差（随着表的增加，性能会直线下降）。 您可以进行优化...

通过保存一些有关每个SourceName选择性的元数据...

CREATE TABLE sourceNameMetaData (
  sourceName  VARCHAR(64),
  occurances  INT
)

我建议使用触发器或其他工具使此表保持最新状态。 然后，您可以按限制性最强的条目过滤ActionTable，然后照常执行其余逻辑。

SELECT
  yourTable.ActionName
FROM
(
  SELECT
    ActionName
  FROM
  (
    SELECT
      sourceName
    FROM
      sourceNameMetaData
    INNER JOIN
      tableWithSourceNames
        ON tableWithSourceNames.SourceName = sourceNameMetaData.SourceName
    ORDER BY
      occurances ASC
    LIMIT
      1
  )
    AS filter    
  INNER JOIN
    yourTable
      ON yourTable.SourceName = filter.SourceName
  GROUP BY
    ActionName
)
  AS filter
INNER JOIN
  yourTable
    ON yourTable.ActionName = filteredData.ActionName
INNER JOIN
  tableWithSourceNames
    ON yourTable.SourceName = tableWithSourceNames.SourceName
GROUP BY
  yourTable.ActionName
HAVING
  COUNT(DISTINCT yourTable.SourceName) = (SELECT COUNT(DISTINCT SourceName) FROM tableWithSourceNames)

笔记：

• 小表不需要此优化
• 此优化假设您同时在两个索引（sourceName，ActionName）和（actionName，sourceName）上具有索引
• 这是一个很棒的例子，我用来证明更多的代码可以更快

Answer 2

SELECT ActionName 
FROM LogTable 
WHERE SourceName IN ('S01', 'S02')
GROUP BY ActionName
HAVING COUNT(DISTINCT SourceName) = 2

要么：

SELECT ActionName 
FROM 
    ( SELECT DISTINCT ActionName
      FROM LogTable
    ) AS dn 
WHERE 
    EXISTS
      ( SELECT *
        FROM LogTable AS a
        WHERE a.ActionName = dn.ActionName
          AND a.SourceName = 'S01'
      )
  AND
    EXISTS
      ( SELECT *
        FROM LogTable AS b
        WHERE b.ActionName = dn.ActionName
          AND b.SourceName = 'S02'
      )

Answer 3

也许我没听错，但是如果您想要的结果是您所显示的内容，那么您无需进行分组或任何其他操作。

select distinct ActionName from YourTable 
where SourceName in ('S01', 'S02')