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0 pointsSatvikBeri14y ago0 comments

SQL equivalent: "Explain the difference between a left join and a full join."

...seriously, this filters out a depressing number of people who put SQL on their resume and are applying for a SQL job.

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7 comments · 3 top-level

mkramlich14y ago· 2 in thread

There are a lot of people who've used SQL, and therefore will think it's perfectly honest and accurate to list SQL experience on their resume, and who've written perfectly fine queries to get shit done, and yet they would not be able to answer that question, especially in an interview/interrogation situation.

Also, in real life, under normal working conditions, we live in the Age of Google (and books) -- if someone ever needed to know the definition, or recite a definition or comparison of those terms, he could just look it up. A better question would be: can they solve problems? And solve them in good ways? And have they in the past? Do they get shit done? Ship? Reliable? Work well with others (to the extend it would matter, because it varies)? Would it be a net win to them involved with your project/team/company? Those questions matter the most by far. And I don't think it's wise to assume they're going to be able to recite a definition of any particular term. Offhand. In a stressful and unnatural situation like an interview.

hnal94314y ago

There's a still a certain level of familiarity with the subject matter required to do a job. If the role can be defined as an "SQL job" (say something in data warehousing or reporting) - not knowing what types of joins are available could lead to terrible solutions.

I would agree with you if the interview question was more specific, say about Oracle window functions for example.

An SQL developer not familiar with full joins would be similar to a Java developer who is not familiar with interfaces, or a Javascript developer who has never heard of closures. It's a significant part of the language, not a piece of arcane reference.

SatvikBeriOP14y ago

You know, that's a fair point. I think our company may be making that same mistake where instead of trying to find the good candidates, we're trying to filter out the bad ones. I'll see if I can change that.

fendale14y ago· 2 in thread

What is a full join? I've been working with Oracle for 10 years and I've never used that term. I know what a left join is and an outer join, but not a full join.

McGlockenshire14y ago

"Conceptually, a full outer join combines the effect of applying both left and right outer joins. Where records in the FULL OUTER JOINed tables do not match, the result set will have NULL values for every column of the table that lacks a matching row."

http://en.wikipedia.org/wiki/Join_(SQL)#Full_outer_join

bricestacey14y ago

It's an outer join.

AncientPC14y ago

I don't use SQL very often, but I've found Jeff Atwood's explanation using Venn diagrams sticks in my memory pretty well:

http://www.codinghorror.com/blog/2007/10/a-visual-explanatio...

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