Sql query Error: Operand should contain 1 column(s) in rails - sql

Question

SELECT *
FROM jobs
WHERE (SELECT DISTINCT jobs.*
FROM jobs, job_requests
WHERE (jobs.user_id = 1) OR
(job_requests.user_id = 1 AND job_requests.job_id = jobs.id)
)
This sql gives me:
Mysql::Error: Operand should contain 1 column(s).
If I execute the select from the where clause it works
SELECT DISTINCT jobs.* FROM jobs, job_requests
WHERE (jobs.user_id = 1) OR
(job_requests.user_id = 1 AND job_requests.job_id = jobs.id)
Could somebody explain me why? This query is generated by rails activerecord so the main select is needed.
The ror code:
has_many :my_jobs, :class_name=>"Job", :finder_sql =>
'SELECT DISTINCT jobs.* ' +
'FROM jobs, job_requests ' +
'WHERE (jobs.user_id = #{id}) OR ' +
'(job_requests.user_id = #{id} AND job_requests.job_id = jobs.id AND job_requests.request_status IN ("requested", "confirmed") )'

Answer 1

I am submitting my answer based on the additional information provided. The query below should address your requirement.
Job.all(:conditions=> [ "
jobs.user_id = ? OR
EXISTS (
SELECT *
FROM job_requests AS B
WHERE B.job_id = jobs.id AND B.user_id = ?
)", user_id, user_id ]
)
If you want an efficient version of the same query then you should go with UNIONs.
sql = "
SELECT *
FROM jobs A WHERE A.user_id = ?
UNION
SELECT *
FROM jobs A, job_requests B
WHERE A.id = B.job_id AND B.user_id = ?
"
Job.find_by_sql(Job.send(:sanitize_sql_array, [sql, user_id, user_id]))
The first query can be converted to a named_scope.
class Job < ActiveRecord::Base
named_scope :for_user, lambda { |user_id| { :conditions=> [ "
jobs.user_id = ? OR
EXISTS (
SELECT *
FROM job_requests AS B
WHERE B.job_id = jobs.id AND B.user_id = ?
)", user_id, user_id ] }
}
end
Now you can use the named_scope as follows:
Jobs.for_user(current_user)

Answer 2

SQL query: Documentation
SELECT (
'95.86.122.224', NOW( ) , '95.86.122.224', '95.86.122.224'
)
FROM orders
LEFT JOIN visitors ON visitors.ip = '95.86.122.224'
WHERE visitors.ip IS NULL
LIMIT 0 , 30
MySQL said: Documentation
#1241 - Operand should contain 1 column(s)

Answer 3

If I have understood you correctly you need to restructure as
SELECT * FROM jobs
WHERE EXISTS
(SELECT DISTINCT jobs.*
FROM jobs, job_requests
WHERE (jobs.user_id = 1)
OR (job_requests.user_id = 1 AND job_requests.job_id = jobs.id))
I'm guessing you only want to select from jobs where the inner query is true, the above will do this for you.

Answer 4

Following code will work, if you want to get the jobs with job requests for a given user:
Job.all( :joins => :jobs_requests,
:conditions => ["job_requests.user_id = ?", user_id])