Join works only if the files being joined share a common field.

join只有在所要连接的文件共享某个共同的域时才会工作。

youdao

As of this writing, YQL doesn't allow you to link tables through common keys (a join), but only permits you to use the results of one query inside another (a subquery).

在撰写本文时，YQL还不允许您通过公用键(一个联接)来链接表，只允许您在一个查询(一个子查询)内使用另一个查询的结果。

youdao

THE British are unfit to join the common market because they differ “profoundly” from continental Europeans, Charles de Gaulle declared in 1963.

1963年查尔斯•戴高乐宣称英国人不配加入共同市场，因为他们与欧陆人有根本差异。

youdao

Is it possible for us to join hands in common effort?

VOA: special.2009.06.05

What used to be unorthodox career paths are becoming more and more common: many join the startup fever and launch their own ventures.

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The committee has suggested that it should only be optional for a two year transitional period, becoming compulsory thereafter for large cross-border companies, with small businesses being forced to join a common system after a further five years.

BBC: Corporate tax debate

However, the problem say the bankers is that in the absence of some kind of entente between the banking class and political class, the banks continue to feel discombobulated, and that makes it harder for them to join the common struggle to rebuild our economy (bankers, of course, say this more in sorrow, rather than as a threat).

BBC: Slim chance of bank bonus deal