[英]MySQL - getting SUM of MAX results from 2 tables
Here's my problem: I have 2 identical tables (past month data, current month data) - data_2010_03, data_2010_04: 这是我的问题:我有2个相同的表(过去月数据,当月数据)-data_2010_03,data_2010_04:
Content_type (VARCHAR), content_id (INT), month_count (INT), pubDate (DATETIME)
Data in month_count is updated hourly, so for each combination of content_type
and content_id
we insert new row, where value of month_count
is incrementally updated. month_count中的数据每小时更新一次,因此对于content_type
和content_id
每种组合,我们插入新行,其中month_count
值将递增更新。
Now I try something like this: 现在我尝试这样的事情:
SELECT MAX(t1.month_count) AS max_1, MAX(t2.month_count) AS max_2, SUM(max_1 + max_2) AS result, t1.content_type, t1.content_id
FROM data_2010_03 AS t1
JOIN data_2010_04 AS t2 ON t1.content_type = t2.content_type AND t1.content_id = t2.content_id
WHERE t2.pubDate < '2010-04-08' AND t1.content_type = 'video'
GROUP BY t1.content_id
ORDER BY result desc, max_1 desc, max_2 desc
LIMIT 0,10
I get an error "Unknown column 'max_1' in 'field list'. Please help. 我收到一个错误“字段列表中的未知列'max_1'。请帮助。
You can not use aliases in expressions (on the same level of select) so 您不能在表达式中使用别名(在选择级别相同),因此
SUM(max_1 + max_2) AS result
has to be written as 必须写成
MAX(t1.month_count)+MAX(t2.month_count) AS result
Instead of 代替
SELECT MAX(t1.month_count) AS max_1, MAX(t2.month_count) AS max_2, SUM(max_1 + max_2) AS result
Can you just do 你能做
SELECT MAX(t1.month_count) + MAX(t2.month_count) AS result
Or I may have misunderstood the requirement. 否则我可能会误解了该要求。
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