Question

我有这样的查询 -

    SELECT 
  CONCAT(u.name, u.deviceAlias),
  u.name,
  u.deviceAlias,
  j.description,
  u.description AS vlanDescription 
FROM
  vlaninterfaces u,
  interfacedescriptioninfo j 
WHERE u.interfacedescriptioninfoid = j.id
  AND u.deviceId = j.deviceId 
  AND u.interfaceNameAlias = j.name 
  AND j.toDevice NOT IN 
  (SELECT 
    deviceAlias 
  FROM
    devices 
  WHERE siteId = 12) 
  AND u.deviceAlias IN 
  (SELECT 
    deviceAlias 
  FROM
    devices 
  WHERE siteId = 12) 
  AND CONCAT(u.name, u.deviceAlias) NOT IN 
  (SELECT DISTINCT 
    CONCAT(v.name, fromDevice) 
  FROM
    vlaninterfaces v,
    interfacedescriptioninfo i 
  WHERE v.interfacedescriptioninfoid = i.id
    AND v.deviceId = i.deviceId 
    AND v.interfacenameAlias = i.name 
    AND v.deviceAlias IN 
    (SELECT 
      deviceAlias 
    FROM
      devices 
    WHERE siteId = 12) 
    AND v.interfacenameAlias LIKE '%ae%' 
    AND IF(
      i.toDevice IS NULL,
      i.interconnectedDevice,
      i.toDevice
    ) IN 
    (SELECT 
      deviceAlias 
    FROM
      devices 
    WHERE deviceClass = 'SWITCH' 
      AND siteId = 12)) 
GROUP BY CONCAT(u.name, u.deviceAlias) ;

我尝试使用MINUS但是在mysql中发现我们不能使用这样的set运算符。

在Explain plan中，表vlaninterfaces不使用键并扫描所有行。

请让我知道NOT IN的替代示例（如果可能的话，同样的查询）。

Answer 1

您的查询非常复杂，所以我只展示部分内容。可以将JOFT JOIN挂到表上并检查null而不是使用NOT IN。即如果我们有查询：

 SELECT 
  CONCAT(u.name, u.deviceAlias),
  u.name,
  u.deviceAlias,
  j.description,
  u.description AS vlanDescription 
FROM
  vlaninterfaces u,
  interfacedescriptioninfo j 
WHERE u.interfacedescriptioninfoid = j.id
  AND u.deviceId = j.deviceId 
  AND u.interfaceNameAlias = j.name 
  AND j.toDevice NOT IN 
  (SELECT 
    deviceAlias 
  FROM
    devices 
  WHERE siteId = 12)

然后我们可以使用siteId 12加入设备别名，并检查where子句中的连接是否成功（请注意下面的示例我也将vlaninterfaces和interfacedescriptioninfo上的连接更改为显式 - 我发现这更具可读性）：

SELECT 
  CONCAT(u.name, u.deviceAlias),
  u.name,
  u.deviceAlias,
  j.description,
  u.description AS vlanDescription 
FROM
  vlaninterfaces u
  INNER JOIN interfacedescriptioninfo j ON (u.interfacedescriptioninfoid = j.id AND u.deviceId = j.deviceId AND u.interfaceNameAlias = j.name )
  LEFT JOIN devices da ON (j.toDevice = da.deviceAlias AND da.siteId = 12)
WHERE 
   da.deviceAlias IS NULL

Answer 2

好的，这需要大量的试验和错误，但我总是尝试将IN子句重写为连接，从而避免使用隐式子查询。同样适用于NOT IN，你可以用LEFT JOIN + WHERE替换为NULL

SELECT 
  CONCAT(u.name, u.deviceAlias),
  u.name,
  u.deviceAlias,
  j.description,
  u.description AS vlanDescription 
FROM
  vlaninterfaces u 
  JOIN   interfacedescriptioninfo j ON u.interfacedescriptioninfoid = j.id AND u.deviceId = j.deviceId AND u.interfaceNameAlias = j.name 
  JOIN devices d2 ON d2.deviceAlias=u.deviceAlias AND d2.siteId=12
  LEFT JOIN devices d1 ON d1.deviceAlias=j.toDevice AND d1.siteId = 12
  LEFT JOIN  (SELECT DISTINCT v.name, fromDevice
              FROM
              vlaninterfaces v,
              JOIN  interfacedescriptioninfo i ON v.interfacedescriptioninfoid = i.id   AND v.deviceId = i.deviceId   AND v.interfacenameAlias = i.name 
              JOIN devices d3 ON d3.deviceAlias=v.deviceAlias AND d3.siteId=12
              JOIN devices d4 ON d4.deviceAlias=IF(i.toDevice IS NULL,  i.interconnectedDevice,  i.toDevice) AND d4.siteId=12 AND d4.deviceClass = 'SWITCH' 
              WHERE v.interfacenameAlias LIKE '%ae%' 
            ) as subquery ON u.name=subquery.name AND u.deviceAlias=subquery.fromDevice

WHERE d1.deviceAlias is NULL -- this replaces the first NOT IN
and subquery.name is NULL  -- this replaces the second NOT IN

通过两个字段的concat查询实际上是丢弃索引。你不需要这样做。

最后，通过concat of name和deviceAlias进行分组在这里没有意义，因为你在select中没有任何聚合函数。

我如何在mysql中优化此查询？

2 个答案: