Question

我正在使用以下查询返回具有相同名字和姓氏的所有重复记录。诀窍是contact_id必须按降序排列。

查询按预期返回联系人，但它只是如此缓慢！检查大约30,000条记录时大约需要6-8秒。

我将contact_firstName，contact_lastName，contact_client_id和contact_id全部编入索引。

我有什么想法可以尝试加快一点速度？谢谢你的帮助：）

SELECT z.contact_id, z.contact_firstName, z.contact_lastName, RIGHT(z.contact_lastName,1) AS nameNum
FROM (`contacts` x) 
JOIN `contacts` z ON `x`.`contact_firstName` = `z`.`contact_firstName` 
AND x.contact_lastName = z.contact_lastName 
AND x.contact_client_id = ".$ID." 
AND z.contact_client_id = ".$ID." 
WHERE `x`.`contact_id` < `z`.`contact_id` 
GROUP BY `z`.`contact_id`

Answer 1

没有做出任何承诺，但这是尝试的替代方案：

SELECT c.contact_id, c.contact_firstName, c.contact_lastName, RIGHT(c.contact_lastName,1) AS nameNum
    FROM (SELECT contact_firstName, contact_lastName, MIN(contact_id) AS MinID
              FROM contacts
              WHERE contact_client_id = ".$ID."
              GROUP BY contact_firstName, contact_lastName
              HAVING COUNT(*) > 1) t
        INNER JOIN contacts c
            ON t.contact_firstName = c.contact_firstName
                AND t.contact_lastName = c.contact_lastName
                AND c.contact_client_id = ".$ID."
                AND t.MinID <> c.contact_id

Answer 2

SELECT z.contact_id, z.contact_firstName, z.contact_lastName
, RIGHT(z.contact_lastName,1) AS nameNum
FROM `contacts` x
JOIN `contacts` z ON (x.contact_client_id = z.contact_client_id)
WHERE `x`.`contact_id` < `z`.`contact_id` 
And x.contact_client_id = '$id'
GROUP BY `z`.`contact_id`

确保您有索引：
- contact_id。
- contact_client_id

加速MySQL连接以检查重复项

2 个答案: