Rails 4在raw activerecord查询中获取列名

Question

I have some code that looks like the following:

query = <<-EOF
        select player_id, first_name, last_name,
            max(case when site_id = 1 then salary end) fd_salary,
            max(case when site_id = 2 then salary end) dd_salary,
            max(case when site_id = 3 then salary end) ss_salary,
            max(case when site_id = 4 then salary end) ds_salary,
            max(case when site_id = 7 then salary end) dk_salary,
            max(case when site_id = 8 then salary end) elite_salary
            from player_salaries ps
            where ps.gamedate = '2014-05-25'
            and sport_id = #{$MLB_SPORT_ID}
            group by player_id
    EOF

        salaries = PlayerSalary.connection.execute(query)

The problem is salaries in this case comes back as an array with values. These query is a bit complex and the names I'm using such as fd_salary , dd_salary and so forth aren't physical attributes in the PlayerSalary model. There's no way to do something like salaries.first.fd_salary . Is there a way to change the above in Rails 4 to get it access values by column name?

Answer 1

You could use find_by_sql for this:

find_by_sql(sql, binds = [])

Executes a custom SQL query against your database and returns all the results. The results will be returned as an array with columns requested encapsulated as attributes of the model you call this method from. If you call Product.find_by_sql then the results will be returned in a Product object with the attributes you specified in the SQL query.

So if you did:

salaries = PlayerSalary.find_by_sql(query)

then you could say things like salaries.first.fd_salary . Just don't try to use columns that weren't in your query or try to change the returned PlayerSalary objects and expect anything useful to happen.

Answer 2

If you want to retrieve your records as a hash, with column names you can use mysql2 adapter directly with:

ActiveRecord::Base.connection.instance_variable_get('@connection').query("SELECT * FROM `users`", as: :hash).first

I was searching for another way to do it but had no luck.