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MathGroup Archive 2006

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Re: Re: How to do a SQL type operation???

  • To: mathgroup at smc.vnet.net
  • Subject: [mg64419] Re: [mg64392] Re: How to do a SQL type operation???
  • From: Richard Palmer <mapsinc at bellatlantic.net>
  • Date: Thu, 16 Feb 2006 03:05:31 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Thanks Ray and others.  I was also able to do solve the problem with a
dispatch command.  Figured it out after I sent the note.

On 2/15/06 3:32 AM, "Ray Koopman" <koopman at sfu.ca> wrote:

> Richard Palmer wrote:
>> Assume Table1={{a,Xa},{b,Xb},...,{n,Xn},...} where the key a can occur many
>> times and Xa is different each occurrence.
>> 
>> We also have table2={{a,Ya},{b,Yb},...,{n,Yn}}. Here a,b,...,n occur exactly
>> once.
>> 
>> How do I create table3={{a,Xa,Ya},{b,Xb,Yb},...,{n,Xn,Yn},...} by joining
>> the tables on the first column?
>> 
>> From the problem, if a (or b or c or ...  n} is in table1, it is also in
>> table1 and visa versa.
>> 
>> The a,b,...,n,... Are small positive integers.
>> 
>> Thanks
> 
> Ah, the virtues of testing! In this case it showed
> the need to parenthesize the function in Scan.
> 
> In[1]:= table1 = {{a,Xa},{b,Xb},{c,Xc},{d,Xd},{a,Xaa},{c,Xcc}}
>       table2 = {{a,Ya},{b,Yb},{c,Yc},{d,Yd}}
>       Module[{Y},Scan[(Y@#[[1]] = #[[2]])&, table2];
>                  Append[#, Y@#[[1]] ]& /@ table1]
> 
> Out[1]= {{a,Xa},{b,Xb},{c,Xc},{d,Xd},{a,Xaa},{c,Xcc}}
> Out[2]= {{a,Ya},{b,Yb},{c,Yc},{d,Yd}}
> Out[3]= {{a,Xa,Ya},{b,Xb,Yb},{c,Xc,Yc},{d,Xd,Yd},
>        {a,Xaa,Ya},{c,Xcc,Yc}}
> 


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