From: Jamey Cribbs <jcribbs@...>
Date: 2005-11-13T13:36:01+09:00
Subject: Re: KirbyBase 2.3: How to insert record if key does not exist

basi wrote:

>Hello,
>
>I have a word frequency table, thus:
>
>tgl_tokens = db.create_table(
>:tgltokens,
>:tgltoken, :String,
>:count, :Integer)
>
>With data from a hash, I'm trying to insert a record into the table,
>but only if the key does not exist in the table. If it does, then add
>the new frequency count into the stored frequency count.
>
> tgl_texts.select.each do |t|
>   freq = Hash.new(0)
>   for word in t.text.to_s.downcase.tr_s('^A-Za-z-',' ').split(' ')
>      freq[word] += 1
>   end
>   freq.delete("")
>
>   freq.each do |w,c|
>      -- if w exists in tgl_tokens, then
>      --   add c to the stored count value of w
>     -- else
>          tgl_tokens.insert do |token|
>            token.tgltoken = w
>            token.count = c
>          end
>     -- end
>   end
>end
>
>Basically the KirbyBase / Ruby syntax that eludes me corresponds to
>this SQL snippet:
>
>begin
>  select 1 into v_dummy
>    from tgltokens
>    where tgltoken = w;
>-- if found then
>    update tgltokens
>      set count = count + c
>      where tgltoken = w;
>exception
>  when no_data_found then
>    insert into tgltokens values (w, c);    
>end
>  
>
If I understand you correctly, you would simply do this:

freq.each do |w,c|
    if tgl_tokens.select { |token| token.tgltoken == w }.size > 0
        tgl_tokens.update { |token| token.tgltoken == w }.set do |token| 
            token.count += c 
        end
    else 
        tgl_tokens.insert do |token|
            token.tgltoken = w
            token.count = c
        end
    end
end

Jamey Cribbs