I'm creating an aggregate from a anstime column in a view table in Denodo and I'm using a Cast to convert it to float and it works only for those numbers with period (example 123.123) but does not work for the numbers without period (example 123). Here's my code which only works for those numbers with period:
SELECT row_date,
case
when sum(cast(anstime as float)) is null or sum(cast(anstime as float)) = 0
then 0
else sum(cast(anstime as float))
end as xans
FROM table where anstime like '%.%'
group by row_date
Can someone please help me how to handle those without period?
My guess is you've got values in anstime which are are not numeric, hence why not having the where anstime like '%.%' predicate causes a failure, as has been mentioned in other comments.
You could try adding in an intermediate view before this one which strips out any non numeric values (leaving the decimal point character of course) and this might then allow you to not have to use the where anstime like '%.%' filter.
Perhaps the REGEXP function which would possibly help there
Your where anstime like '%.%' clause is going to restrict possible responses to places where anstime has a period in it. Remove that if you want to allow all values.
I appreciate those who responded to my concern. In the end we had to reach out to our developers to fix the data type of the column from varchar to float rather than doing a workaround.
I got a table named companies and a column named employees, which is a string column.
My where condition to find companies which have between 10 and 100 employees:
where("companies.employees >= ? AND companies.employees <= ?", 10, 100)
The problem is: The column needs to remain a string column so I can't just convert it to integer but I also want to compare the employee numbers. Is there any way to do this?
This may work, it is a ruby question, I don't know ruby :-) In postgres I would write the query as Craig says, like this:
select * from companies where employees::integer >= 10 and employees::integer <= 100;
(Of course there is substitution, etc, but this gets the concept across. One of the problems you run in to when you don't use the correct type in postgres is that indices don't work right. Since you are casting the employees to an integer type, you have to fetch every record, convert it to an integer, then filter using the greater/less than stuff. Every record in the table will be fetched, casted, then compared. If this was an integer type to start with, and there was an index on the table, then the postgres engine can do a lot better performance wise by selecting only the relevant records. Anyway...
Your ruby may work modified like this:
where("companies.employees::integer >= ? AND companies.employees::integer <= ?", 10, 100)
But, that makes me curious about the substitution. If the type is gleaned from the type of the argument, then it might work because the 10 and 100 are clearly integers. If the substitution gets weird, you might be able to do this:
where("companies.employees::integer >= cast(? as integer) AND companies.employees::integer <= cast(? as integer)", 10, 100)
You can use that syntax for the entire query as well:
where("cast(companies.employees as integer) >= cast(? as integer) AND cast(companies.employees as integer) <= cast(? as integer)", 10, 100)
One of these variants might work. Good Luck.
-g
I have two different tables, which if time was taken could be made more similar or even combined but for convenience sake they are currently different. They both have an id column and a start_date column which is of type datetime.
I'm trying to think of a way that's not extremely convoluted or without using custom sql to get and sort the result into one sorted array using the start_date column.
Can anyone think of a quick way to do it? The tables have no active record relation at all.
Thanks
Yes, the simplest way to do this would be
#objects = Duck.all + Quack.all
# Oldest first
#objects.sort! { |a, b| a.start_date <=> b.start_date }
# Newest first
#objects.sort! { |a, b| b.start_date <=> a.start_date }
This:
- book.prices.order(:currency_code).each do |price|
returns all a book's prices ordered alphabetically by currency code:
AUD 19.99
GBP 9.99
NZD 26.00
USD 14.95
Now, how can I neatly get GBP to always appear at the top of the list, with the others sorting alphabetically, like this:
GBP 9.99
AUD 19.99
NZD 26.00
USD 14.95
This answer shows the SQL solution, but I'm not sure about the Rails way.
Since ordering is normally done on DB level, just use the SQL solution in rails:
- book.prices.order("`currency_code` = 'GBP' desc, currency_code").each do |price|
you can use sql snippets in Rails (ActiveRecord) query methods.
Depending on your DB you might have to choose the right SQL solutiuon, so probably
- book.prices.order("CASE WHEN currency_code = 'GBP' THEN 1 ELSE 2 END, currency_code").each do |price|
works in your case.
You can check the resulting sql in rails console:
book.prices.order("CASE WHEN currency_code = 'GBP' THEN 1 ELSE 2 END, currency_code").to_sql
and check, whether it works in you DB.
An other way is of cause to add an extra column for sorting, this way you can even position commonwelth currencies in front of others etc.
I already have a working solution, but I would really like to know why this doesn't work:
ratings = Model.select(:rating).uniq
ratings.each { |r| puts r.rating }
It selects, but don't print unique values, it prints all values, including the duplicates. And it's in the documentation: http://guides.rubyonrails.org/active_record_querying.html#selecting-specific-fields
Model.select(:rating)
The result of this is a collection of Model objects. Not plain ratings. And from uniq's point of view, they are completely different. You can use this:
Model.select(:rating).map(&:rating).uniq
or this (most efficient):
Model.uniq.pluck(:rating)
Rails 5+
Model.distinct.pluck(:rating)
Update
Apparently, as of rails 5.0.0.1, it works only on "top level" queries, like above. Doesn't work on collection proxies ("has_many" relations, for example).
Address.distinct.pluck(:city) # => ['Moscow']
user.addresses.distinct.pluck(:city) # => ['Moscow', 'Moscow', 'Moscow']
In this case, deduplicate after the query
user.addresses.pluck(:city).uniq # => ['Moscow']
If you're going to use Model.select, then you might as well just use DISTINCT, as it will return only the unique values. This is better because it means it returns less rows and should be slightly faster than returning a number of rows and then telling Rails to pick the unique values.
Model.select('DISTINCT rating')
Of course, this is provided your database understands the DISTINCT keyword, and most should.
This works too.
Model.pluck("DISTINCT rating")
If you want to also select extra fields:
Model.select('DISTINCT ON (models.ratings) models.ratings, models.id').map { |m| [m.id, m.ratings] }
Model.uniq.pluck(:rating)
# SELECT DISTINCT "models"."rating" FROM "models"
This has the advantages of not using sql strings and not instantiating models
Model.select(:rating).uniq
This code works as 'DISTINCT' (not as Array#uniq) since rails 3.2
Model.select(:rating).distinct
Another way to collect uniq columns with sql:
Model.group(:rating).pluck(:rating)
If I am going right to way then :
Current query
Model.select(:rating)
is returning array of object and you have written query
Model.select(:rating).uniq
uniq is applied on array of object and each object have unique id. uniq is performing its job correctly because each object in array is uniq.
There are many way to select distinct rating :
Model.select('distinct rating').map(&:rating)
or
Model.select('distinct rating').collect(&:rating)
or
Model.select(:rating).map(&:rating).uniq
or
Model.select(:name).collect(&:rating).uniq
One more thing, first and second query : find distinct data by SQL query.
These queries will considered "london" and "london " same means it will neglect to space, that's why it will select 'london' one time in your query result.
Third and forth query:
find data by SQL query and for distinct data applied ruby uniq mehtod.
these queries will considered "london" and "london " different, that's why it will select 'london' and 'london ' both in your query result.
please prefer to attached image for more understanding and have a look on "Toured / Awaiting RFP".
If anyone is looking for the same with Mongoid, that is
Model.distinct(:rating)
Some answers don't take into account the OP wants a array of values
Other answers don't work well if your Model has thousands of records
That said, I think a good answer is:
Model.uniq.select(:ratings).map(&:ratings)
=> "SELECT DISTINCT ratings FROM `models` "
Because, first you generate a array of Model (with diminished size because of the select), then you extract the only attribute those selected models have (ratings)
You can use the following Gem: active_record_distinct_on
Model.distinct_on(:rating)
Yields the following query:
SELECT DISTINCT ON ( "models"."rating" ) "models".* FROM "models"
In my scenario, I wanted a list of distinct names after ordering them by their creation date, applying offset and limit. Basically a combination of ORDER BY, DISTINCT ON
All you need to do is put DISTINCT ON inside the pluck method, like follow
Model.order("name, created_at DESC").offset(0).limit(10).pluck("DISTINCT ON (name) name")
This would return back an array of distinct names.
Model.pluck("DISTINCT column_name")