如何使用一个查询从两个表中选择数据 [英] How to select data from two tables using a single query

问题描述

我一直在设法了解如何使用单个查询从我的两个表中选择数据.如果有人能提出比单次查询更好的方法，那我真是无所适从！以前，我会使用两个查询来做到这一点，尽管我被认为是一个查询会更好，所以我尝试学习.

I've been trying to get my head around how to use a single query to select data from two of my tables. If anybody can suggest a better way than a single query, I'm all ears! Previously I would do this using two queries which I could make work easily although I'm led to believe that a single query would be better, hence trying to learn.

我的一张桌子很像这个表格.将此表称为成员":

One of my tables resembles this in a cut down form. Call this table "member":

ID  |  firstName  |   lastName  | networkingID

还有另一个我称为网络"的表:

And the other table which I'll call "networking":

ID  |  websiteURL | facebookURL | twitterURL

我想做的是在表member上运行查询，例如:

What I'm trying to do is run a query on the table member like:

SELECT * FROM `member` WHERE `ID`=2

从表member返回数据.

但是，我也希望从表networking中返回相关值.表member中的列networkingID是networking中行的ID.

However I also wish to return the relating value from the table networking. The column networkingID in the table member is the ID of the row in networking.

我该怎么做?

到目前为止，我已经尝试过使用可以通过Google找到的所有JOIN，但无法使其正常运行.我最好的结果是使用LEFT JOIN，其中所有列均存在，但联网表的结果均为NULL.

So far, I have experimented using all of the JOINs that I was able to find through Google but I am unable to make it work. My best result was with a LEFT JOIN where all of the columns were present but the results from the networking table were all NULL.

推荐答案

SELECT * FROM member
LEFT JOIN networking
ON member.networkingID=networking.ID
WHERE member.ID=2

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