mysql 查询连接/内部连接
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mysql query join/inner join
提问by Steeve
i have two tables in my mysql i want to extract the results based on combined query for both tables. i tried join as well as inner join but no success the structure of
我的 mysql 中有两个表，我想根据两个表的组合查询提取结果。我尝试加入以及内部加入但没有成功的结构
tableA is
表A是
id userid topic
1 34 love
3 64 friendship
35 574 romance
32 253 games
95 633 football
54 26 cricket
648 63 music
tableB is
表B是
id location username
34 Australia krkrff
64 india dieiei
574 pakistan frkfrf
253 japan frfffrk
633 india ifirf
26 Australia riiri
63 Australia frffjrr
Please note that in tableA userid and in TableB id is same .both reflect the data of same users.i want to display tableA data by filtering location column from tableB. suppose that i want to display topic of tableB and the users belongs to Australia then it should give output :love cricket music
请注意 tableA 中的 userid 和 TableB 中的 id 是相同的。两者都反映了相同用户的数据。我想通过过滤 tableB 中的位置列来显示 tableA 数据。假设我想显示 tableB 的主题并且用户属于澳大利亚，那么它应该给出输出：love cricket music
you can see in tableB that 34,26 & 63 belongs to Australia so the output is like that. if the location is india then outpput will be
您可以在 tableB 中看到 34,26 & 63 属于澳大利亚，因此输出是这样的。如果位置是印度，那么输出将是
friendship and football.please tell how to write sql query.
友谊和足球。请告诉如何编写sql查询。
回答by Paul Bellora
The following should select what you're describing:
以下应选择您所描述的内容：
select a.topic
from tableA a
join tableB b on b.id = a.userid
where b.location = 'Australia' -- or whichever location you filter on
which is equivalent to:
这相当于：
select a.topic
from tableA a
join tableB b on b.id = a.userid and b.location = 'Australia'
回答by Gabriel Santos
SELECT a.topic, b.topic FROM tableA a, tableB b WHERE a.id = b.id AND b.location = 'Australia'
回答by Rohan Durve
Could you please elaborate on what you mean by "tableA userid and in TableB id is same", because they are visible different such that we cannot use them as keys.
您能否详细说明“tableA 用户 ID 和 TableB 中的 ID 相同”是什么意思，因为它们的可见性不同，因此我们不能将它们用作键。
As I understand it however, you'd prolly want to do a JOIN and then a SELECT only for the TOPIC.
但是，据我了解，您肯定会想要对 TOPIC 执行 JOIN 和 SELECT 操作。
So, your query should be:
所以，你的查询应该是：
SELECT t1.topic from table1 t1 JOIN tableB t2 on t2.id = t1.id WHERE t2.location = 'Australia'
回答by Mohammad Saberi
Try this:
尝试这个：
SELECT tableA.topic FROM tableA JOIN tableB
ON tableA.userid = tableB.id
WHERE tableB.location = 'Australia';
