This must be a basic thing in rails, but I don't know how to do it.
I would like to filter participants based on the languages they speak. People can speak multiple languages, and languages are stored in their own table with a one-to-many relationship.
Now my search looks really clunky and doesn't seem to work:
if #cvsearch.language.present? == true and #cvsearch.language != 0
#p = #p.joins(:languages).where('languages.name = ?', #cvsearch.language)
else
#cvsearch.language = 0
end
if #cvsearch.language1.present? == true and #cvsearch.language1 != 0
#p = #p.joins(:languages).where('languages.name = ?', #cvsearch.language1)
end
if #cvsearch.language2.present? == true and #cvsearch.language2 != 0
#p = #p.joins(:languages).where('languages.name = ?', #cvsearch.language2)
end
if #cvsearch.language3.present? == true and #cvsearch.language3 != 0
#p = #p.joins(:languages).where('languages.name = ?', #cvsearch.language3)
end
The resulting SQL, slightly shortened:
SELECT COUNT(*) FROM "participants" INNER JOIN "languages" ON "languages"."participant_id" = "participants"."id" WHERE (participants.id >= 2) AND (languages.name = 11) AND (languages.name = 10)[0m
It would be great to get a specific solution, but even better is a pointer as to where I can read up on this - what's the key word I am missing to describe this problem?
So this is the solution I am using for now:
if #cvsearch.language1.present? == true and #cvsearch.language1 != 0
safe_lang = ActiveRecord::Base::sanitize(#cvsearch.language1)
qry = "INNER JOIN languages l1 ON l1.participant_id = participants.id AND l1.name = " + safe_lang.to_s
#p = #p.joins(qry)
end
Works wonderfully, just need to get some feedback regarding the safety of this approach.
I'm not sure of a general reference to refer you to, but this is basic SQL stuff. Basically, the JOIN is performed first resulting in a number of rows and then the WHERE is applied, filtering the rows. The conceptual mistake here is thinking that the WHERE clause will somehow apply to the full set of matched languages, but it doesn't work that way, each row of the result is considered in isolation, therefore a clause like (languages.name = 11) AND (languages.name = 10) will never return anything, because languages.name only has a single value in each row. The query as constructed could only work for an OR clause, so you could say something like WHERE (languages.name = 11) OR (languages.name = 12).
In order to filter down the participants you need one join for each language, so you want something like this:
SELECT COUNT(*) FROM participants
INNER JOIN languages l1 ON l1.participant_id = participants.id AND (languages.name = 10)
INNER JOIN languages l2 ON l2.participant_id = participants.id AND (languages.name = 11)
WHERE participants.id >= 2
Offhand I'm not sure of the easiest way to do this in ActiveRecord, it's not a super common query. Your general structure should work, but with something like:
if #cvsearch.language1.present? == true and #cvsearch.language1 != 0
safe_language = ActiveRecord::Base.sanitize(#cvssearch.language1)
join_clause = "INNER JOIN languages l1 ON l1.participant_id = participants.id AND language.name = #{safe_language}"
#p = #p.joins(join_clause)
end
Related
Basically I'd like to return all people whose current job title is X and whose previous job title is Y. As an example, I have a talent whose current emnployment is "Airbnb (company_id = 1)" and whose previous employment is at "Youtube (company_id = 2)".
If I run a query to find talent where current employment is Airbnb:
Talent.joins(:job_histories).where(["job_histories.company_id = ? and job_histories.end_year = ?", 1, "Present"])
I get the person.
If I run a query where previous employment is Youtube (hence the end_year != "Present" below)
Talent.joins(:job_histories).where(["job_histories.company_id = ? and job_histories.end_year != ?", 2, "Present"])
I also get the same person.
However, if I chain them together to find talents where current employer is Airbnb AND previous employer is Youtube, like this:
#talents = Talent.all
#talents = #talents.joins(:job_histories).where(["job_histories.company_id = ? and job_histories.end_year = ?", 1, "Present"])
#talents = #talents.joins(:job_histories).where(["job_histories.company_id = ? and job_histories.end_year != ?", 2, "Present"])
I do not get any results. I've tried several variations of the query but none return anything.
The only way I can get it to work is by using the first query and then looping over each talent to find where job_histories.company_id == 2.
if params[:advanced_current_company] && params[:advanced_previous_company]
#talents = #talents.joins(:job_histories).where(job_histories: { company_id: params[:advanced_current_company] }).distinct if params[:advanced_current_company]
#talents.each do |talent|
talent.job_histories.each do |job_history|
if job_history.company_id == params[:advanced_previous_company][0].to_i
new_talents.append(talent.id)
end
end
end
#talents = Talent.where(id: new_talents)
end
Any direction would be amazing. Thanks!
You had the right idea with a double join of the job_histories, but you need to alias the job_histories table names to be able to differentiate between them in the query, as otherwise activerecord will think it's only one join that needs to be done.
Talent.joins("INNER JOIN job_histories as jh1 ON jh1.talent_id = talents.id")
.joins("INNER JOIN job_histories as jh2 ON jh2.talent_id = talents.id")
.where("jh1.company_id = ? and jh1.end_year = ?", 1, "Present")
.where("jh2.company_id = ? and jh2.end_year != ?", 2, "Present")
Assume I have an arbitrary number of Group records and I wanna query User record which has_many :groups, the catch is that users are queries by two bound fields from the groups table.
At the SQL level, I should end up with something like this:
SELECT * FROM users where (categories.id = 1 OR users.status = 0) OR(categories.id = 2 OR users.status = 1) ... -- to infinity
This is an example of what I came up with:
# Doesn't look like a good solution. Just for illustration.
or_query = groups.map do |g|
"(categories.id = #{g.category.id} AND users.status = #{g.user_status.id} )"
end.join('OR')
User.joins(:categories).where(or_query) # Works
What I think I should be doing is something along the lines of this:
# Better?
or_query = groups.map do |g|
"(categories.id = ? AND users.status = ? )".bind(g.category.id, g.user_status.id) #Fake method BTW
end.join('OR')
User.joins(:categories).where(or_query) # Works
How can I achieve this?
There has to be a better way, right?
I'm using Rails 4.2. So the shiny #or operator isn't supported for me.
I would collect the condition parameters separately into an array and pass that array (splatted, i.e. as an arguments list) to the where condition:
or_query_params = []
or_query = groups.map do |g|
or_query_params += [g.category_id, g.user_status.id]
"(categories.id = ? AND users.status = ?)"
end.join(' OR ')
User.joins(:categories).where(or_query, *or_query_params)
Alternatively, you might use ActiveRecord sanitization:
or_query = groups.map do |g|
"(categories.id = #{ActiveRecord::Base.sanitize(g.category_id)} AND users.status = #{ActiveRecord::Base.sanitize(g.user_status.id)})"
end.join(' OR ')
User.joins(:categories).where(or_query)
I have an array of conditions i'm passing to where(), with the conditions being added one at a time such as
conditions[:key] = values[:key]
...
search = ModelName.where(conditions)
which works fine for all those that i want to compare with '=', however I want to add a '<=' condition to the array instead of '=' such as
conditions[:key <=] = values[:key]
which of course won't work. Is there a way to make this work so it i can combine '=' clauses with '<=' clauses in the same condition array?
One way of doing it:
You could use <= in a where clause like this:
User.where('`users`.`age` <= ?', 20)
This will generate the following SQL:
SELECT `users`.* FROM `users` WHERE (`users`.`age` <= 20)
Update_1:
For multiple conditions, you could do this:
User.where('`users`.`age` <= ?', 20).where('`users`.`name` = ?', 'Rakib')
Update_2:
Here is another way for multiple conditions in where clause:
User.where('(id >= ?) AND (name= ?)', 1, 'Rakib')
You can add any amount of AND OR conditions like this in your ActiveRecord where clause. I just showed with 2 to keep it simple.
See Ruby on Rails Official Documentation for Array Conditions for more information.
Update_3:
Another slight variation of how to use Array Conditions in where clause:
conditions_array = ["(id >= ?) AND (name = ?)", 1, "Rakib"]
User.where(conditions_array)
I think, this one will fit your exact requirement.
You could use arel.
conditions = {x: [:eq, 1], y: [:gt, 2]}
model_names = ModelName.where(nil)
conditions.each do |field, options|
condition = ModelName.arel_table[field].send(*options)
model_names = model_names.where(condition)
end
model_names.to_sql --> 'SELECT * FROM model_names WHERE x = 1 and y > 2'
I am using rails 4 for developing my application. I have a problem in my active record query with not equal to condition. I am not getting required output. I think there is a problem with not equal to part.
#available_rooms = Room.joins("LEFT OUTER JOIN reservations ON reservations.room_id = rooms.id").where("category_id = ? AND arrival_date != ?",params[:category],params[:arrival_date])
You can use where.not() in Rails 4 :
#available_rooms = Room.joins("LEFT OUTER JOIN reservations ON reservations.room_id = rooms.id")
.where(category_id: params[:category])
.where.not(arrival_date: params[:arrival_date])
In some version of SQL not equal is written as !=
Try this using the comparator <> like so:
#available_rooms = Room.joins("LEFT OUTER JOIN reservations ON reservations.room_id = rooms.id")
.where("category_id = ? AND arrival_date <> ?",params[:category],params[:arrival_date])
The real tactical question I am facing is all categories are set as 'default' therefore if I make options[:category] = 'default' it only adds the points that have no category. Therefore if i add points to cateogry 'arin' it will not be counted to the 'default' total. So I tried to grab all tables if NOT NULL or by category but it keeps grabbing the same amount for 'arin'.
default: 20
arin: 20
Should be total of 40 if category not supplied or at 'default', if params category 'arin' then it should be 20.
Can someone help me understand the concept behind the correct SQL to get the results I am looking for?
New to rails and SQL.
def self.top_scored(options = {})
options[:table_name] ||= :users
options[:since_date] ||= 4.months.ago
options[:end_date] ||= 1.month.from_now
options[:category] ||= nil
options[:limit] ||= 10
alias_id_column = "#{options[:table_name].to_s.singularize}_id"
if options[:table_name] == :sashes
sash_id_column = "#{options[:table_name]}.id"
else
sash_id_column = "#{options[:table_name]}.sash_id"
end
# MeritableModel - Sash -< Scores -< ScorePoints
sql_query = <<SQL
SELECT
#{options[:table_name]}.id AS #{alias_id_column},
SUM(num_points) as sum_points
FROM #{options[:table_name]}
LEFT JOIN merit_scores ON merit_scores.sash_id = #{sash_id_column}
LEFT JOIN merit_score_points ON merit_score_points.score_id = merit_scores.id
WHERE merit_score_points.created_at > '#{options[:since_date]}' AND merit_score_points.created_at < '#{options[:end_date]}' AND (merit_scores.category IS NOT NULL OR merit_scores.category = '#{options[:category]}')
GROUP BY #{options[:table_name]}.id, merit_scores.sash_id
ORDER BY sum_points DESC
LIMIT #{options[:limit]}
SQL
results = ActiveRecord::Base.connection.execute(sql_query)
results.map do |h|
h.keep_if { |k, v| (k == alias_id_column) || (k == 'sum_points') }
end
results
end
end
Seems no one answered and only down voted. Here is to anyone that questions this in the future. I figured out you can split sql statements and use an if statement in rails around the SQL.
sql_query = "SELECT
#{options[:table_name]}.id AS #{alias_id_column},
SUM(num_points) as sum_points
FROM #{options[:table_name]}
LEFT JOIN merit_scores ON merit_scores.sash_id = #{sash_id_column}
LEFT JOIN merit_score_points ON merit_score_points.score_id = merit_scores.id
WHERE merit_score_points.created_at > '#{options[:since_date]}' AND merit_score_points.created_at < '#{options[:end_date]}' "
if(options[:category] != nil)
sql_query += "AND merit_scores.category = \"#{options[:category]}\" "
end
sql_query += "GROUP BY #{options[:table_name]}.id, merit_scores.sash_id
ORDER BY sum_points DESC
LIMIT #{options[:limit]} "
results = ActiveRecord::Base.connection.execute(sql_query)