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MySql inner join four tables

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  • 27-10-2014 8:53pm
    #1
    Scrappychimow
    Closed Accounts Posts: 1,040 ✭✭✭


    Hi I have four tables
    Table 1 : column1= day,column2=time

    Table 2 : column1=rain, column2=temperature

    Table 3: column1=firstinitial, column2=lastinitial

    Table 4: column1=firstinitial, column2=lastinitial

    I am not sure what the statement should say to inner join all four tables (must use inner join)

    SELECT rain,day,time,temperature,firstinitial,lastinitial INNER JOIN ??


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    #2
    deconduo
    Moderators, Computer Games Moderators Posts: 4,281 Mod ✭✭✭✭deconduo


    That question doesn't make much sense. Generally if you are doing joins on tables there needs to be a common column to join on.

    Have a read of this, it should help:

    http://www.w3schools.com/sql/sql_join_inner.asp


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    #3
    Scrappychimow
    Closed Accounts Posts: 1,040 ✭✭✭Scrappychimow


    deconduo wrote: »
    That question doesn't make much sense. Generally if you are doing joins on tables there needs to be a common column to join on.

    I know it has me puzzled, any idea of how to join the tables using another form of join or union etc?


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    #4
    deconduo
    Moderators, Computer Games Moderators Posts: 4,281 Mod ✭✭✭✭deconduo


    Scrappychimow wrote: »
    I know it has me puzzled, any idea of how to join the tables using another form of join or union etc?

    Why do you want to do a join on those particular tables, what sort of data are you trying to pull back?


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    #5
    Scrappychimow
    Closed Accounts Posts: 1,040 ✭✭✭Scrappychimow


    i made a mistake i dont need to join four tables, but still need to get that data using inner join


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    #6
    keith16
    Closed Accounts Posts: 8,061 ✭✭✭keith16


    deconduo wrote: »
    That question doesn't make much sense. Generally if you are doing joins on tables there needs to be a common column to join on.

    Have a read of this, it should help:

    http://www.w3schools.com/sql/sql_join_inner.asp

    This link is very helpful OP, definitely read it and try the examples using your own data.
    Scrappychimow wrote: »
    i made a mistake i dont need to join four tables, but still need to get that data using inner join

    The data in your OP bears no relation to what you posted in the word doc...so I think we are all a bit confused.

    Joins are fairly straightforward once you get used to them.

    SELECT

    [Column1]
    ,[Column2]

    etc....

    FROM myfirstable A

    INNER JOIN mysecondtable B

    ON A.Common_Column_Table1 = B.Common_Column_Table2

    A and B are aliases for your tables so MySQL knows which column you are referring to if there are columns in both tables with the same name.

    Have a look at this too. Should help.

    Joins work because you have columns in more than one table that contain the same data / information, so SQL can display information from more than 1 table by linking a common field / column.


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    #7
    el pibe
    Registered Users Posts: 24 ✭el pibe


    It's not looking like an especially useful data model at first glance.

    Traditionally data in and RDBMS is related (hence the term). We usually do this by providing an artificial key an id) but natural keys are fine.
    The data should obviously reflect the real world thing you're trying to model though.

    A join generally follows this relationship between tow tables. In your case, perhaps, between a weather record, a weather type(?) and some sort of person record, twice?

    Could you describe what it is you're trying to achieve, and perhaps definitions of the full tables along with their names?.

    If things were clearer we could help.


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