Forum: Ruby Best gem for an existing mysql database

Hi,

I've an existing MySql database, and not having used any of the major 
database gems like ActiveRecord, Sequel etc etc I was wondering which 
one would work well against an already built DB ?

The quicker I can get up and running the better. It would also be nice 
if I could bypass whatever sugar it has to run SQL directly, so I can 
just plug in any exising queries that are lying around.


Any help on this is much appreciated.

Regards,
Iain

On 04/28/2011 05:24 AM, Iain Barnett wrote:
> Hi,
>
> I've an existing MySql database, and not having used any of the major database 
gems like ActiveRecord, Sequel etc etc I was wondering which one would work well 
against an already built DB ?
>
> The quicker I can get up and running the better. It would also be nice if I 
could bypass whatever sugar it has to run SQL directly, so I can just plug in any 
exising queries that are lying around.

Sequel and AR will both let you drop to the SQL level, if the model
level isn't quite right for what you want to do. I don't know about
DataMapper or other ORMs.

One thing I've always liked about sequel is that there is an
intermediate level, between models and SQL: datasets with their chained
query methods. Some examples:

http://cheat.errtheblog.com/s/sequel

The documentation for datasets:

http://sequel.rubyforge.org/rdoc/files/doc/dataset...

Rather than use models, I often find it easier to think in relational
terms and code in ruby, and that's what sequel's datasets let you do.

Another factor to consider, when the database precedes the app, is
whether the ORM layer supports the schema. IIUC, AR doesn't support
composite primary keys without using an extra library. Sequel does
support composite primary keys (this was very helpful to my team just in
the last few weeks). This difference may not matter much, but it's
something to be aware of.

More on sequel's differences from AR:

http://sequel.rubyforge.org/rdoc/files/doc/active_...

On 28 Apr 2011, at 20:42, Joel VanderWerf wrote:
>
> Another factor to consider, when the database precedes the app, is whether the 
ORM layer supports the schema. IIUC, AR doesn't support composite primary keys 
without using an extra library. Sequel does support composite primary keys (this 
was very helpful to my team just in the last few weeks). This difference may not 
matter much, but it's something to be aware of.

This is a deal breaker, or maker in this case as the database does hold 
several composite keys.

>
> Rather than use models, I often find it easier to think in relational terms and 
code in ruby, and that's what sequel's datasets let you do.

I think this would suit my style of thinking too. I'm quite comfortable 
with SQL and sets and they seem to make more sense for a lot of problems 
than starting with objects, for me anyway.

>
>
> More on sequel's differences from AR:
>
> http://sequel.rubyforge.org/rdoc/files/doc/active_...

Thanks, I'll give those a look. I really appreciate the time you've 
taken to give me a good answer, it's difficult to tell from just reading 
the docs / looking at examples, as they all *seem* to do what you want, 
and right now I don't have the time to get far down the road before 
failing.

Thanks again.

Regards,
Iain

Iain

Here is an ORM that works with MySQL
https://www.kellermansoftware.com/p-47-net-data-ac...