So i have two tables, Table 1 and Table 2
In Table 1 there is a column called event name
In Table 2 there is a column called description
Now the issue I'm having is I am needing to link rows together, the issue is one of the event names shows as this:
xyz presents: The Alphabet and Friends
And the description shows as
Alphabet and Friends
So the issue im having is i'm trying it like this:
Table2.where("description LIKE ?", "%xyz presents: The Alphabet and Friends%")
And the above is not finding anything as i expected, If i removed the first 3 words, it matches but i cannot trust this as a solution.
Any recommendations on how to fix this?
Searching with LIKE works as expected. It seems that you expect it to somehow know which words to ignore it it's match which it doesn't. Why can't you just do?
Table2.where("description LIKE ?", "%The Alphabet and Friends%")
If you need to search a few terms you could do:
Table2.where("description LIKE ? or description LIKE ?",
"%The Alphabet and Friends%", "%xyz presents:%")
Related
I don't know the name for this kind of search, but I see that it's getting pretty common.
Let's say I have records with the following file names:
'order_spec.rb', 'order.sass', 'orders_controller_spec.rb'
If I search with the following string 'oc' I would like the result to return 'orders_controller_spec.rb' due to match the o in orders and the c in controller.
If the string is 'os' then I'd like all 3 to match, 'order_spec.rb', 'order.sass', 'orders_controller_spec.rb'.
If the string is 'oco' then I'd like 'orders_controller_spec.rb'
What is the name for this kind of search and how would I go about getting this done in Postgresql?
This is a called a subsequence search. One simple way to do it in Postgres is to use the LIKE operator (or several of the other options in those docs) and fill the spaces between your letters with a wildcard, which for LIKE is %. To match anything with an o followed by an s in the words column, that would look like this:
SELECT * FROM table WHERE words LIKE '%o%s%';
This is a relatively expensive search, but you can improve performance with a varchar_pattern_ops or text_pattern_ops index to support faster pattern matching.
CREATE INDEX pattern_index ON table (words varchar_pattern_ops);
In my app I have invoice numbers like this:
2014.DEV.0001
2014.DEV.0002
2014.TSZ.0003
The three character code is a company code. When a new invoice number needs to be assigned it should look for the last used invoice number for that specific company code and add one to it.
I know the company code, I use a LIKE to search on a partial invoice number like this:
last = Invoice.where("invoice_nr LIKE ?", "#{DateTime.now.year}.#{company_short}.").last
This results in this SQL query:
SELECT "invoices".* FROM "invoices" WHERE "invoices"."account_id" = 1 AND (invoice_nr LIKE '2014.TSZ.') ORDER BY "invoices"."id" DESC LIMIT 1
But unfortunately it doesn't return any results. Any idea to improve this, as searching with LIKE doesn't seem to be correct?
Try wrapping string with % and use lower to convert the query string and result into downcase to avoid any wrong results due to case, try this
last = Invoice.where("lower(invoice_nr) LIKE lower(?)", "%#{DateTime.now.year}.#{company_short}.%").last
You want % for partial match
last = Invoice.where("invoice_nr LIKE ?", "%#{DateTime.now.year}.#{company_short}.%").last
Since you want to match only the left part you need to add one % at the right part of your string
Invoice.where("invoice_nr LIKE ?", "#{DateTime.now.year}.#{company_short}.%").last
In my application a User has Highlights.
Each Highlight has a HighlightType. So if I run user.highlights I might see an output like this:
Notice that there are many highlights of type_id 47. This marks milestones of the number of times the user has gone running.
What I would like to do is return this full list of records, but only include one highlight for each highlight_type, and I want that one record to be the most recent record (in this case the "50th run" highlight). So in the example above I would get the same results but with IDs 195-199 removed.
Is there an efficient way to accomplish this?
I don't think there is an easy or clean way to achieve that, nor a "Rails way". Look at e.g. this link
According to one suggestion in that link you would do this SQL request:
SELECT h1.*
FROM highlights h1
LEFT JOIN highlights h2
ON (h1.user_id = h2.user_id
AND h1.highlight_type_id = h2.highlight_type_id
AND h1.created_at < h2.created_at)
WHERE h2.id IS NULL AND h1.user_id = <the user id you are interested in>
group by h1.highlight_type_id
I think it will be some performance problem if you have big tables maybe, an it not so very clean I think.
Otherwise, if there isn't so much highlights for a user I would have done something like this:
rows = {}
user.highlights.order('highlight_type_id, created_at DESC').each do |hi|
rows[hi.highlight_type_id] ||= hi
end
# then use rows which will have one object for each highlight_type_id
The DESC on created_at is important
EDIT:
I also saw some suggestions based on this
user.highlights.group('highlight_type_id').order('created_at DESC')
And that was also how I first thought it should be solved, but I tested it and it doesn't seems to get a correct result - at least on my test data.
I have a table with 1 million+ records that contain names. I would like to be able to sort the list by the first letter in the name.
.. ABCDEFGHIJKLMNOPQRSTUVWXYZ
What is the most efficient way to setup the db table to allow for searching by the first character in the table.name field?
The best idea right now is to add an extra field which stores the first character of the name as an observer, index that field and then sort by that field. Problem is it's no longer necessarily alphabetical.
Any suggestions?
You said in a comment:
so lets ignore the first letter part. How can I all records that start with A? All A's no B...z ? Thanks – AnApprentice Feb 21 at 15:30
I issume you meant How can I RETURN all records...
This is the answer:
select * from t
where substr(name, 1, 1) = 'A'
I agree with the questions above as to why you would want to do this -- a regular index on the whole field is functionally equivalent. PostgreSQL (with some new ones in v. 9) has some rather powerful indexing capabilities for special cases which you might want to read about here http://www.postgresql.org/docs/9.1/interactive/sql-createindex.html
No matter what language I'm using I always need to display a list of strings separated by some delimiter.
Let's say, I have a collection of products and need to display its names separated by ', '.
So I have a collection of Products, where each one has a 'name' attribute. I'm looking for some Rails method/helper (if it doesn't exist, maybe you can give me ideas to build it in a rails way) that will receive a collection, an attribute/method that will be called on each collection item and a string for the separator.
But I want something that does not include the separator at the end, because I will end with "Notebook, Computer, Keyboard, Mouse, " that 2 last characters should not be there.
Ex:
concat_ws(#products, :title, ", ")
#displays: Notebook, Computer, Keyboard, Mouse
Supposing #products has 4 products with that names of course.
Thanks!
you should try the helper to_sentence.
If you have an array, you can do something like
array.to_sentence. If your array has the data banana, apple, chocolate it will become:
banana, apple and chocolate.
So now if you have your AR Model with a field named, you could do something like
MyModel.all.map { |r| r.name }.to_sentence
#products.map(&:title).join(', ')
As #VP mentioned, Array#to_sentence does this job well in rails. The code for it is here:
https://github.com/rails/rails/blob/master/activesupport/lib/active_support/core_ext/array/conversions.rb
Saying that, its use of the Oxford Comma is questionable :-)