Jeremy Evans wrote:
> On May 28, 10:38 pm, Joel VanderWerf <[email protected]> wrote:
>> (1) why does
>>
>> entries = items.where("id" => id)
>>
>> fail, when "id" is apparently an acceptable substitute for :id in #<< ?
>
> Because "id" in the filter is an SQL string. If you want an SQL
> identifier, you should use :id.
So the contents of that hash key could potentially be some other SQL
string besides a column name? Or is this just for column names with
spaces, symbols, etc.?
> The only reason "id" works in insert/
> << is that you can't use an SQL string in its place, so it assumes you
> mean an identifer:
>
> UPDATE items SET 'id' = 3; -- Invalid SQL
>
> items.where(:id => id) # WHERE id = 3
> items.where('id' => id) # WHERE 'id' = 3
>
> In general you should always use symbols for SQL identifiers (columns/
> tables) when you are using Sequel.
Makes sense. I tend to prefer strings as keys in YAML (and by necessity
JSON) documents, so I'll just get used to always interning, when the key
is not a literal.
>> (2) Is there a way to express the if... as a single operation, with the
>> same semantics (i.e. not failing when there's already an entry)?
>
> If you are using MySQL, you can use:
>
> ds[:items].replace(:id=>id)
>
> That'll use a single REPLACE query. REPLACE isn't standard SQL
> though, and I don't think any other adapters support it. Models have
> a find_or_create method which does something similar. Your way isn't
> a bad way to do things.
Ok, I don't feel so clumsy now. Thanks!
--
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407
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