# Searching with a collection

**URL:** <https://www.ruby-forum.com/t/searching-with-a-collection/86084>\
**Category:** Rails\
**Created:** [February 19, 2007, 7:32pm UTC](https://www.ruby-forum.com/t/searching-with-a-collection/86084 "2007-02-19T19:32:47Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![technodolt](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/e99b99/32.png) [@technodolt](https://www.ruby-forum.com/u/technodolt)\
**Post date:** [February 19, 2007, 7:32pm UTC](https://www.ruby-forum.com/t/searching-with-a-collection/86084/1 "2007-02-19T19:32:47Z")

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If I want to find all rows in a table where a field matches one of  
several possible values, what is the most efficient way to do it?

So I have table groups, with field idcode  
I have idcodes = [143, 482, 941]  
I’m guessing I should do:

find(:all, :conditions =\> idcodes.collect {|id| “idcode = #{id}”}.join("  
OR "))

Oh, and I suppose instead of making two posts, since they are directly  
related, I can just ask another question here also:

I’m going to be getting the array of idcodes from another table, called  
idents.

Something like table idents, with fields name, code1, code2, idcode.

I want to get an array of all the idcodes where the row fits some other  
condition… should I do this via find(:all, :conditions =\> “code1 = 2  
AND code2 = 4”).collect {|ident| ident.idcode}, or is there some other,  
better way to get an array containing just the values of one field of a  
table, without having to get each record and pull that field from it?

Thanks.

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<div class="post-metadata">

**Author:** ![technodolt](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/e99b99/32.png) [@technodolt](https://www.ruby-forum.com/u/technodolt)\
**Post date:** [February 19, 2007, 8:19pm UTC](https://www.ruby-forum.com/t/searching-with-a-collection/86084/2 "2007-02-19T20:19:18Z")

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> find :all, :conditions =\> [‘idcode IN (?)’, idcodes]
> 
> find(:all, :conditions =\> “…”, :select =\> ‘idcode’).map(&:idcode)
> 
> ```
> -- Jean-Fran�ois.
> 
> ```

Thank you very much 🙂  
Those will both work perfectly.

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<div class="post-metadata">

**Author:** ![technodolt](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/e99b99/32.png) [@technodolt](https://www.ruby-forum.com/u/technodolt)\
**Post date:** [February 19, 2007, 8:11pm UTC](https://www.ruby-forum.com/t/searching-with-a-collection/86084/3 "2007-02-19T20:11:39Z")

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Hi Luke,

> If I want to find all rows in a table where a field matches one of  
> several possible values, what is the most efficient way to do it?
> 
> So I have table groups, with field idcode  
> I have idcodes = [143, 482, 941]  
> I’m guessing I should do:
> 
> find(:all, :conditions =\> idcodes.collect {|id| “idcode = #{id}”}.join("  
> OR "))

find :all, :conditions =\> [‘idcode IN (?)’, idcodes]

is better.

And don’t use string interpolation in tour queries to avoid possible  
SQL injection.

> AND code2 = 4").collect {|ident| ident.idcode}, or is there some other,  
> better way to get an array containing just the values of one field of a  
> table, without having to get each record and pull that field from it?

if you’re only interested in idcode attribute, I can only see to  
fetch only idcode attribute with :select option like this :

find(:all, :conditions =\> “…”, :select =\> ‘idcode’).map(&:idcode)

the map(&:idcode) is the same as your collect … but shorter 🙂

```
  -- Jean-François.

```

–  
Ruby ( [http://www.rubyfrance.org](http://www.rubyfrance.org) ) on Rails ( [http://www.railsfrance.org](http://www.railsfrance.org)  
)