将 INNER JOIN 添加到我的 MySQL 查询中，以便我可以使用 DISTINCT

Question

我正在使用 4 个表 - 项目、主机、历史记录、映射

物品

hostid,itemid,name,valuemapid
10761,304827,Phone 33 44 55 66 77 88:Model of the Phone,68
10761,304827,Phone 33 44 55 66 77 88:Model of the Phone,68
10761,304827,Phone 33 44 55 66 77 88:Model of the Phone,68
10761,304828,Phone 33 44 55 66 88 88:Model of the Phone,68
10761,304828,Phone 33 44 55 66 88 88:Model of the Phone,68
10761,304828,Phone 33 44 55 66 88 88:Model of the Phone,68
10761,304829,Phone 33 44 55 77 77 88:Model of the Phone,68
10761,304829,Phone 33 44 55 77 77 88:Model of the Phone,68
10761,304820,Phone 33 44 44 66 77 88:Model of the Phone,72
10761,304820,Phone 33 44 44 66 77 88:Model of the Phone,72

主机

hostid,name
10761,CUCM2

历史

itemid,value
304827,109
304828,109
304829,109
304829.110

映射

valuemapid,value,newvalue
68,109,Cisco 7841
72,110,Cisco 7940

我写了一个查询来给我手机的型号和该型号的数量，但它正在计算重复项。有人告诉我我需要添加一个 INNER JOIN，但我不知道该怎么做。有人可以帮我更改我的查询以对“Items”表进行 INNER JOIN，以便删除所有重复的 ItemID。

SELECT map.newvalue as 'Model of Phone', Count(*) as 'Number of Phones'
FROM items i, hosts h, history huint, mappings map
WHERE h.hostid=i.hostid AND h.name='$Hosts' AND i.itemid=huint.itemid AND i.valuemapid=map.valuemapid AND huint.value=map.value AND i.name LIKE '%Model of the Phone'
GROUP BY map.newvalue
LIMIT 100;

返回

Model of Phone, Number of Phones
Cisco 7841, 8
Cisco 7940, 2

谢谢！

** UPDATE ** 使用 LEFT JOIN 但不知道如何使用 DISTINCT

SELECT map.newvalue as 'Model of Phone', Count(*) as 'Number of Phones'
FROM hosts h
    LEFT JOIN items i
        ON h.hostid=i.hostid
    LEFT JOIN history_uint huint
        ON i.itemid=huint.itemid
    LEFT JOIN mappings map
        ON i.valuemapid=map.valuemapid
WHERE h.name='$Hosts' AND huint.value=map.value AND i.name LIKE '%Model of the Phone'
GROUP BY map.newvalue
ORDER BY 'Item Name' DESC
LIMIT 100;

Answer 1

这是您使用 1992 年后语法重写的查询...

SELECT m.newvalue 'Model of Phone'
     , Count(*) 'Number of Phones'
  FROM items i
  JOIN hosts h
    ON h.hostid = i.hostid 
  JOIN history y
    ON y.itemid = i.itemid
  JOIN mappings m
    ON m.valuemapid = y.valuemapid 
   AND y.value = m.value
 WHERE h.name = '$Hosts' -- this is insecure
   AND i.name LIKE '%Model of the Phone' -- and this cannot use an index 
 GROUP 
    BY m.newvalue
 ORDER
    BY m.newvalue
 LIMIT 100;

现在，如需进一步帮助，请参阅 Why should I provide an MCVE for what seems to me to be a very simple SQL query?