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我不确定术语，但我现在基本上有一个 2 表左连接，如下所示：

Snippets Table
snippet_id PK
snippet_text

snippets_link_email_id Table
snippet_id * (Links to Snippets Table)
email_id * (Links to emails Table)

emails Table
email_id 
version_no

许多其他各种数据

所以发生的事情是一个日志被解析并插入到 emails 表中，每条记录都有关于日志文本的详细信息，发现的错误和关于用户的各种信息。

我需要从每个日志中获取的主要信息是错误，每个唯一错误都存储在片段表中。

由于可能有许多电子邮件具有相同的错误，我喜欢运行以下查询以查看有多少唯一错误：

$total_exception_check = mysql_query("SELECT * FROM snippets");
$total_exceptions = mysql_num_rows($total_exception_check);

while ($row = mysql_fetch_array($total_exception_check))
{
$i = $row['snippet_id'];
//Need to find total occurrences of this error

$feedback_query = mysql_query("SELECT * FROM snippets LEFT JOIN snippets_link_email_id ON snippets.snippet_id = snippets_link_email_id.snippet_id WHERE snippets_link_email_id.snippet_id = $i AND snippet_date BETWEEN CURRENT_TIMESTAMP - INTERVAL '$num_days' HOUR AND CURRENT_TIMESTAMP");
}
$tot_snippets = mysql_num_rows($feedback_query);

所以我基本上遍历每个独特的错误，然后搜索snippets_link_email_id 表以查看该错误记录了多少次，即有多少已解析的电子邮件出现了该错误。

tot_snippets 告诉我每个的总量。所以这太棒了，我现在可以为每个错误建立一个表格，以及它被记录了多少次。

然而，在 emails 表中有很多信息，包括版本号，如果我想得到 emails 表中 version_no 的值 = 2000 的总唯一错误怎么办

我将如何编辑此代码以查看它？

SELECT *
FROM snippets
LEFT JOIN snippets_link_email_id
    ON snippets.snippet_id = snippets_link_email_id.snippet_id
WHERE
    snippets_link_email_id.snippet_id = $i
    AND snippet_date BETWEEN
        CURRENT_TIMESTAMP - INTERVAL '$num_days' HOUR
        AND CURRENT_TIMESTAMP

我从其他类似的帖子中尝试过这个，但我猜我很远：

 SELECT *
 FROM snippets, emails
 LEFT JOIN snippets_link_email_id
     ON snippets.snippet_id = snippets_link_email_id.snippet_id
     AND snippets_link_email_id.email_id ON emails.email_id
 WHERE snippets_link_email_id.snippet_id = $i
 AND snippet_date BETWEEN
     CURRENT_TIMESTAMP - INTERVAL '$num_days' HOUR AND CURRENT_TIMESTAMP
4

2 回答 2

1

连接多个表的一般形式是

SELECT (columns or collations)
FROM table1
LEFT JOIN table2
ON (some condition that associates rows in table1 with rows in table2)
LEFT JOIN table3
ON (some condition that associates rows in table1 or table2 with rows in table3)
WHERE (whatever you want to limit the result set to)

无论您要加入多少个表，都遵循相同的基本模式，但如果您使用很多表，那么给它们加上别名可能会让您的生活更轻松。

SELECT (columns or collations)
FROM table1 AS t1
LEFT JOIN table2 AS t2
ON (some condition that associates rows in t1 with rows in t2)
LEFT JOIN table3 AS t3
ON (some condition that associates rows in t1 or t2 with rows in t3)
WHERE (whatever you want to limit the result set to)
于 2013-01-23T09:16:00.570 回答
1

正确加入电子邮件会解决它吗？

 SELECT *
 FROM snippets
 LEFT JOIN snippets_link_email_id
 ON snippets.snippet_id = snippets_link_email_id.snippet_id
 LEFT JOIN emails
 ON snippets_link_email_id.email_id = emails.email_id
 WHERE snippets_link_email_id.snippet_id = $i
 AND snippet_date BETWEEN CURRENT_TIMESTAMP - INTERVAL '$num_days' HOUR AND CURRENT_TIMESTAMP");

另外，我注意到您的第一个查询没有使用时间戳。这将返回比你真正需要的更多的行（我猜）。您可以按时间戳过滤第一个查询，然后您的循环将大大减小：

SELECT * FROM snippets
     WHERE snippet_date BETWEEN CURRENT_TIMESTAMP - INTERVAL '$num_days' HOUR AND CURRENT_TIMESTAMP");
于 2013-01-23T09:16:50.503 回答