Understanding INNER join in detail

  • gischimp

    Old Hand

    Points: 363

    First, please ignore the arrogance of those participants who presume to comment on the grammar of your article. I wonder how many of them have mastered more than one language; or, how many of them have bothered to submit articles for submission.

    While I consider correct writing to be important, I view this online forum as a place for professionals to trade information. The currency of topics takes priority over formality. Were this a formal presentation, I would be more particular. Come on, folks, focus on content here.

    To speak to the article's content, I found it an interesting topic. You dispensed with a lot of embellishment and took straight to the point. If readers don't find it an advanced enough topic, perhaps they need a forum for their own advanced level. If it were not worth their time to read I am curious why they took more of their time for to write a reply.

    Personally, I find it useful to speak to fundamental topics. In our work, we often forget to focus on the basics to our detriment.

    Thank you for the article.

  • Former Member

    Grasshopper

    Points: 21

    Gischump is absolutely correct. I apologize for the rude remarks and concur with the earlier post that this should never have been published w/o first being edited. I will cancel my SQL Server Membership immediately.

  • Lord Of SQL

    SSC Veteran

    Points: 260

    Frankly, I found the article utterly unreadable. These aren't typos - this is a fundamental lack of grasp of the language... A language that is at the core of T-SQL. For an article that I hoped would delve deeper than I have into the fine uses of JOIN, it was quite a disappointment.

    I had hoped my first post would be more positive, but alas.

    -----------------------------
    I enjoy queries!

  • jpellman

    Grasshopper

    Points: 12

    Please read your work before publishing content. English is America's language - God bless America!!!

  • jpellman

    Grasshopper

    Points: 12

    Please read your work before publishing content. English is America's language - God bless America!!!

  • Holy One

    SSC Veteran

    Points: 291

    I tend to agree with the poster who said we shouldn't be too harsh on someone whose native tongue isn't English.

    One comment though: put the queries just before you talk about the results; saves having to scroll up and down or split screen or whatever.

    D'Arcy

  • Lord Of SQL

    SSC Veteran

    Points: 260

    I disagree with the entirety of your response. It is not arrogance to point out the utterly poor quality of the article. This is SQLServerCentral.com, not night school. The terrible grammar of the article impacts the ability of the reader to derive information from it. Why SSC would publish it in such a form, I have no idea.

    This is not formality. This is a lack of ability to communicate in written form... Very sloppy. Shame on SSC for allowing this to be published.

    You ask why I reply negatively? Simple. I have come to enjoy and respect the high quality of SSC articles. I want to see THAT continue. If this poor article is the real direction of SSC, you can count me out.

    gischimp (7/8/2008)


    First, please ignore the arrogance of those participants who presume to comment on the grammar of your article. I wonder how many of them have mastered more than one language; or, how many of them have bothered to submit articles for submission.

    While I consider correct writing to be important, I view this online forum as a place for professionals to trade information. The currency of topics takes priority over formality. Were this a formal presentation, I would be more particular. Come on, folks, focus on content here.

    To speak to the article's content, I found it an interesting topic. You dispensed with a lot of embellishment and took straight to the point. If readers don't find it an advanced enough topic, perhaps they need a forum for their own advanced level. If it were not worth their time to read I am curious why they took more of their time for to write a reply.

    Personally, I find it useful to speak to fundamental topics. In our work, we often forget to focus on the basics to our detriment.

    Thank you for the article.

    -----------------------------
    I enjoy queries!

  • Caesar2

    SSC Veteran

    Points: 214

    I have a big question (I guess that is big only for me), but... 'what is the real advantage of INNER JOIN??? why not to use WHERE condition to join tables or to do al the combinations that you did in your article???'

    Thanks a lot.

    (PS: anybody knows if the 'diferences' are the same in al DBMS's???)

  • gischimp

    Old Hand

    Points: 363

    I would only point out that like greg.harter I have not been a participant very long (based solely on points) and I would be very hesitant personally to make such broad characterizations as to the overall quality of SSC. I, too, appreciate the information provided here.

    I'm not paying a subscription, so I don't get too upset about some occasional glitches in standard formal English. Many people from many cultures make valuable posts, perhaps in something other than their native tongue. I would be humiliated to have to post in French, although I studied it. It would take days to sort through all the grammatical and other errors.

    The point being, to get the level of participation required to provide fresh topics daily, no mean feat, SSC may not be able to accept only those entries meeting the full requirements of King's English.

    Likewise, no replies, including my own, meet this standard. The use of abbreviations, shortcuts, etc., seems to be allowed to respondents but not to those who submit articles. Perhaps a double-standard.

    All of this is not even accounting for the difference between the UK form and USA form of English. I'm sure my colleagues in Great Britain could take exception with many of my standard forms of expression.

    I'm not perfect nor do I expect perfection. Too many trees, I fear, have obscured the forest. Your point is well-taken that we should strive to express ourselves carefully and correctly when posting to our colleagues. Let's just not be too full of ourselves, shall we.

  • Jonathan Ben Aharon-381129

    SSC Enthusiast

    Points: 109

    A good article for beginners.

    Actually, many people do not know that 'JOIN' clauses work this way (they know that JOINs work, but they don't know exactly how).

    I will be showing this to junior developers in my company.

    About the silly grammar comments : please grow up people. Or try writing a technical article in a foreign language 😛

  • jim.powers

    SSCrazy Eights

    Points: 8700

    orrego.cesar (7/8/2008)


    I have a big question (I guess that is big only for me), but... 'what is the real advantage of INNER JOIN??? why not to use WHERE condition to join tables or to do al the combinations that you did in your article???'

    Thanks a lot.

    (PS: anybody knows if the 'diferences' are the same in al DBMS's???)

    To understand this, you need to understand the order in which the statement is processed. The FROM clause is processed first. SQL Server (or any RDBMS for that matter) starts with this statement to limit the amount of data returned in the query. From what I have read, I believe you'll find that using INNER JOIN rather than joining in the WHERE clause will be a substantial performance boost since you have already limited the data set before it starts to pull the actual data. This is especially critical when joining multiple tables as it limits the amount of data the query engine has to process when it gets to the WHERE statement.

  • CAGreensfelder

    SSC Eights!

    Points: 919

    When I started following this site a couple of years ago, I would have LOVED to have seen this article. It is very basic, yes, but it is a very clear, straight forward explaination. Is there a "Start here" list for newbies? This should be on it.

    At that time, my co-worker was writing querries and she didn't know half of what was covered in the article. We were a group of developers porting a mainframe CICS application written in PL/1 with a VSAM file system to a Windows app in VB with a SQL back end. Susan didn't know T-SQL from Sanskrit at the begining of the project. I think there is a place here for this sort of introductory material.

    As to grammar errors, I'm perfectly willing to give the guy a break. I noted that English wasn't his first language while reading the article, but probably would have forgotten about if others hadn't made such a big deal.

  • CAGreensfelder

    SSC Eights!

    Points: 919

    Pardon my grammar. Last sentance should read: "..but probably would have forgotten about it if others hadn't made such a big deal. "

  • mtassin

    SSC-Insane

    Points: 23099

    orrego.cesar (7/8/2008)


    I have a big question (I guess that is big only for me), but... 'what is the real advantage of INNER JOIN??? why not to use WHERE condition to join tables or to do al the combinations that you did in your article???'

    Thanks a lot.

    (PS: anybody knows if the 'diferences' are the same in al DBMS's???)

    Join 25+ tables together some time using a list of tables in the FROM clause and all of the join criteria in the WHERE clause mixed with the actual records selection criteria.... SQL 92 introduced us to INNER/LEFT/RIGHT/OUTER JOIN, god bless it for doing so.



    --Mark Tassin
    MCITP - SQL Server DBA
    Proud member of the Anti-RBAR alliance.
    For help with Performance click this link[/url]
    For tips on how to post your problems[/url]

  • Caesar2

    SSC Veteran

    Points: 214

    thanks for your answer jim.powers... but i'm still not clear in this case.

    I don't know if i have to ask in other topic (because i guess that is not exactly the same kind of questions) but... in measurable terms (time, reads)... a 'SELECT * FROM Table1 INNER JOIN Table2 on (Table1.id = Table2.id)' is so different to a 'SELECT * FROM Table1, Table2 WHERE Table1.id=Table2.id'

    Obviously the product of the FROM is different... the final resulset is the same too... but.. when you use a JOIN, are not doing a cartesian product an then a conditional discrimination of rows???

    I don't know HOW works really the JOIN...

    thanks a lot again.

    César.

    PS: I really sorry about my grammar...

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