amvis wrote in post #1037853:
> ok fine, i just used in the rails code, now i got the same output. can u
> give one clarification about that query
>
> Loyalty.find_by_sql("SELECT COUNT(id) as recordcount FROM
> loyalties")*.first.recordcount, * the recordcount is the count.
> *
> *
> here what is this* first.recordcount*
Okay, I'm going to explain this to you, against my better judgement.
However, you're going to have to learn how to answer questions like this
on your own. Otherwise you're never going to become productive as a
programmer...
I'll break the statement into parts:
Part 1:
Loyalty.find_by_sql
This statement is designed to return the results as a collection (Array)
of objects.
Part 2:
.first
Returns the first object contain in the collection returned by
find_by_sql.
Part 3:
.recordcount
This is the method that returns the attribute named in the SQL (as
recordcount). ActiveRecord will create the .recordcount method
dynamically based on the objects it receives from the database.
Again, and as was mentioned in an earlier post. This particular
technique, for this particular query, is completely unnecessary as
Loyalty.count should give you the exact same result, just as efficiently
as writing the SQL yourself.
Example Query:
ruby-1.9.3-p0 :001 > Order.count
The generated SQL:
(0.5ms) SELECT COUNT(*) FROM "orders"
Result:
=> 2
Counting id (assuming id is the primary key of the table) should always
match COUNT(*) since id should NEVER be null.
Using .find_by_sql should be reserved as a last resort. If ActiveRecord
can give you want to want then use what it provides before resorting to
raw SQL queries.
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