Question

是否可以通过一个 MySQL 查询来实现此任务？

表网址。字段{ ID ，网址}

1，www.mysite.kom
2，mysite.kom
3，anothersite.kom

表日志。字段{ ID ， url_id ， group_type - 数字范围为1..10}

1,1,4 2,1,4 3,2,5 4,2,5
5,3,9

此示例中的查询结果应为： 1 （mysite.com和www.mysite.com = 1）

目标：

需要统计日志表中记录的所有不同网址，但有几个条件：

1）包含 www。前缀的网址，如 mysite.kom 和 www.mysite.kom ，被视为 1 （不是2）。

2） group_type 的范围为 4..6

3）现在，任何这些 group_type 4..6 的网址都会被忽略，而不会显示在 group_type 低于4的网址列表中完全算了。

SQL代码：

SELECT COUNT(DISTINCT TRIM(LEADING 'www.' FROM b.url))
FROM logs a
INNER JOIN urls b
ON a.url_id = b.id
WHERE (group_type BETWEEN 4 AND 6) 

----- and this condition below -----

AND TRIM(LEADING 'www.' FROM b.url)
NOT IN (
  SELECT TRIM(LEADING 'www.' FROM b.url)
  FROM logs a
  INNER JOIN urls b
  ON a.url_id = b.id
  WHERE (group_type < 4)
)

如果我的sql查询是正确的，可以优化（看起来更紧凑）吗？

Answer 1

SELECT COUNT(DISTINCT u.id) AS COUNT_QUES FROM urls u
INNER JOIN logs l
ON u.id=l.url_id
WHERE u.url NOT IN (SELECT A.url FROM 
(SELECT * FROM urls u
WHERE SUBSTR(u.url,1,3)!='www')A,
(SELECT * FROM urls v
WHERE SUBSTR(v.url,1,3)='www')B
WHERE A.url=SUBSTR(B.url,5,LENGTH(B.url))
) 
AND l.group_type BETWEEN 4 AND 6
AND u.id NOT IN
(SELECT DISTINCT u.id FROM urls u
INNER JOIN logs l
ON u.id=l.url_id
WHERE u.url NOT IN (SELECT A.url FROM 
(SELECT * FROM urls u
WHERE SUBSTR(u.url,1,3)!='www')A,
(SELECT * FROM urls v
WHERE SUBSTR(v.url,1,3)='www')B
WHERE A.url=SUBSTR(B.url,5,LENGTH(B.url))
) 
AND l.group_type < 4
)

OR

SELECT COUNT(DISTINCT CASE WHEN B.URL_ID IS NOT NULL AND FLAG1 = 1 AND FLAG2 = 0 THEN TRIM(LEADING 'www.' FROM A.URL) END)
FROM URLS A 
LEFT JOIN (SELECT URL_ID,
           MAX(CASE WHEN GROUP_TYPE BETWEEN 4 AND 6 THEN 1 ELSE 0 END) FLAG1,
           MAX(CASE WHEN GROUP_TYPE < 4 THEN 1 ELSE 0 END) FLAG2
           FROM LOGS
           GROUP BY URL_ID) B
           ON A.ID = B.URL_ID

希望这对您有用。请在SQLFIDDLE上查看 - http://sqlfiddle.com/#!2/1fde2/39

Answer 2

这是一种方式：

SELECT trimmed_url
  FROM ( SELECT TRIM(LEADING 'www.' FROM urls.url) AS trimmed_url,
                MIN(logs.group_type) AS min_group_type
           FROM logs
           JOIN urls
             ON urls.id = logs.url_id
          GROUP
             BY trimmed_url
       ) t
 WHERE min_group_type BETWEEN 4 AND 6
;

但只有你可以判断它是否看起来更紧凑，只有测试可以判断它是否表现更好。

MySQL查询 - 优化

2 个答案: