我有以下两个表格:
Reviews table
id
user_id
review
title
datetime
PeopleFollows table
id
user_id
following_user_id
datetime
我想提出1点询问,以便及时取得10大成果。 例如,如果我有以下数据:
审查表
1 user1 "This is my review" "title" 2011-01-10
2 user1 "Another review" "title again" 2011-01-08
后续表
1 user2 user1 2011-01-09
我想取得这样的结果:
Review id=2
People follows id=1
Review id = 1
我认为,我这样做的唯一途径是单独提出X限额问题,然后将它们合并起来,以取得X结果。
I might need to explain a little more.
如果你按日期对表格进行索引,并且按时间在UNION之前按时间顺序排列,你就不需要全扫描。
(SELECT "Review", id, datetime FROM Reviews ORDER BY datetime DESC LIMIT 10)
UNION
(SELECT "People", id, datetime FROM PeopleFollows ORDER BY datetime DESC LIMIT 10)
ORDER BY datetime DESC
LIMIT 10
You can use UNION, but query won t be optimal:
(SELECT "Review", id FROM Reviews)
UNION
(SELECT "People", folowing_user_id FROM PeopleFollows)
ORDER BY datetime DESC
LIMIT 10
您不能在座标中使用适当的指数,可以全心全意。 因此,在你自己的风险下使用。
更好的想法——不要试图合并表格。 用于此目的的第三轴线。
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