If I have the following query, is it possible to be able to run a function inside? Let's say I want to add WHERE zip_code = user_distance(zip_code)?
I want to take data from each row and run it through a function before actually selecting it.
#posts = Listing.find_by_sql(["SELECT * FROM listings WHERE industry = ? && ", current_user.industry])
If you are mainly looking to get this working and not worrying so much about performance (because going straight to the SQL is faster than going through ActiveRecord) then you could do:
listings = []
Listing.all.each do |listing|
listings << listing if user_distance(listing.zip_code)
end
So, it will go through each listing and add it to that array if the user_distance method returns true (or however it is set up).
Another thing you could do is set up a stored procedure ("stored proc") on your database that takes in a zip code and returns what it is you want (i.e, does the same thing as user_distance), and that user defined variable max_distance could be in a database table so it's accessible to your stored procedure. Then you could call that stored proc from the SQL and still be able to pass in the zip_code of each row.
Related
I want to accomplish a fairly simple task (I'd think).
I have one table with a shiftid (INT), shiftstart (datetime), shiftend (datetime).
I'd like to query that table, then run a query (on an entirely different database) that asks for production (which is calculated in an odd way - requiring three separate queries) using the start and end times, and store that in the original database with the shiftid and a production amount for the shift.
I've tried to do this using a Foreach Loop and a script task that builds a variable that would contain the query, but I'm continually hitting a brick wall there.
Dts.Variables("User::SQLshiftstart").Value = "SELECT value FROM[dbo].[AnalogHistory] WHERE TagName = 'Z_HISTFMZ_P2_0004' AND DateTime = '" & Dts.Variables("User::shiftstart").ToString
I keep getting an error - "Command text was not set for the command object". And googling that error doesn't push me any further down the path.
Help!
Well, I decided to go a different way instead of using a script object to build a variable. I actually created the variable in my SELECT:
SELECT (CONCAT
('SELECT CAST(value AS DECIMAL(10,4)) AS beg FROM [dbo].[AnalogHistory] WHERE TagName = ''Z_HISTDATA_P1_0007'' AND DateTime = '' ',
DateAdd(hh,-6,shiftstart),
' '' AND wwTimeZone = ''UTC'' '))
This way, I avoid having to build an intermediate script object and can directly query based on the variable name in my FOREACH loop.
I have some reporting methods throughout my app and in some cases I want to return the count (for a dashboard), and in others, return the full result set for viewing the details of a report.
What I'm wondering, is there a way to dynamically choose to show the count (instead of what I'm doing here):
def get_query_results(reporting_parameters, count_only = true)
#put together reporting details...
if count_only
MyModel.where(query).count
else
MyModel.where(query)
end
end
I considered setting a local variable to the result of my query parameter, and then call count, but that queries the database again (and even if it didn't it could increase memory usage).
Is there a way to do an effective way to do this in one query? This is one of several queries I have like this in my app, otherwise I wouldn't care. Also, I'd use a ternary, but the actual query conditions in my app are much longer than my example here and it makes it unreadable.
Suppose you are doing this:
#collection = get_query_results(...)
Then you can do this afterwards instead of inside of the action:
#collection.count
And if you like to call another method:
def total_number(collection)
collection.count
end
#collection = get_query_results(...)
no_of_records = total_number(#collection)
I'm having a strange issue.
I created a model observer for my user model. The model observer is being run at 'saving'. when I dump the object at the very end of the user model to be displayed ( this is just before it saves.. according to laravel docs ) it displays all the attributes set correctly for the object, I've even seen an error that showed the correct attributes as set and being inserted into my database table. However, after the save has been completed and I query the database, two of the fields are not saved into the table.
There is no code written by myself sitting between the point where I dumped the attributes to check that they had been set and the save operation to the database. so I have no idea what could be causing this to happen. All the names are set correctly, and like I said, the attributes show as being inserted into the database, they just never end up being saved, I receive no error messages and only two out of ten attributes aren't being saved.
In my searches I have found many posts detailing that the $fillable property should be set, or issues relating to a problem with variables being misnamed or unset, however because I already have the specific attributes not being saved specified in the $fillable array, on top of the fact that they print out exactly as expected pre save, I don't believe those issues are related to the problem I am experiencing.
to save I'm calling:
User::create(Input::all());
and then the observer that handles the data looks like this:
class UserObserver {
# a common key between the city and state tables, helps to identify correct city
$statefp = State::where('id',$user->state_id)->pluck('statefp');
# trailing zeros is a function that takes the first parameter and adds zeros to make sure
# that in this case for example, the dates will be two characters with a trailing zero,
# based on the number specified in the second parameter
$user->birth_date = $user->year.'-'.$user->trailingZeros( $user->month, 2 ).'-'.$user->trailingZeros( $user->day, 2 );
if(empty($user->city)){
$user->city_id = $user->defaultCity;
}
$user->city_id = City::where( 'statefp', $statefp )->where('name', ucfirst($user->city_id))->pluck('id');
# if the user input zip code is different then suggested zip code then find location data
# on the input zip code input by the user from the geocodes table
if( $user->zip !== $user->defaultZip ){
$latlon = Geocode::where('zip', $user->zip)->first();
$user->latitude = $latlon['latitude'];
$user->longitude = $latlon['longitude'];
}
unset($user->day);
unset($user->month);
unset($user->year);
unset($user->defaultZip);
unset($user->defaultCity);
}
that is the code for the two values that aren't being set, when I run
dd($user);
all the variables are set correctly, and show up in the mysql insert attempt screen with correct values, but they do not persist past that point.. it seems to me that possibly mysql is rejecting the values for the city_id and the birth_date. However, I cannot understand why, or whether it is a problem with Laravel or mysql.
since I was calling
User::create();
I figured I'd try to have my observer listen to:
creating();
I'm not sure why it only effected the date and city variables, but changing the function to listen at creating() instead of saving() seems to have solved my problem.
I have the following query
#initial_matches = Listing.find_by_sql(["SELECT * FROM listings WHERE industry = ?", current_user.industry])
Is there a way I can run another SQL query on the selection from the above query using a each do? I want to run geokit calculations to eliminate certain listings that are outside of a specified distance...
Your question is slightly confusing. Do you want to use each..do (ruby) to do the filtering. Or do you want to use a sql query. Here is how you can let the ruby process do the filtering
refined list = #initial_matches.map { |listing|
listing.out_of_bounds? ? nil : listing
}.comact
If you wanted to use sql you could simply add additional sql (maybe a sub-select) it into your Listing.find_by_sql call.
If you want to do as you say in your comment.
WHERE location1.distance_from(location2, :units=>:miles)
You are mixing ruby (location1.distance_from(location2, :units=>:miles)) and sql (WHERE X > 50). This is difficult, but not impossible.
However, if you have to do the distance calculation in ruby already, why not do the filtering there as well. So in the spirit of my first example.
listing2 = some_location_to_filter_by
#refined_list = #initial_matches.map { |listing|
listing.distance_from(listing2) > 50 ? nil : listing
}.compact
This will iterate over all listings, keeping only those that are further than 50 from some predetermined listing.
EDIT: If this logic is done in the controller you need to assign to #refined_list instead of refined_list since only controller instance variables (as opposed to local ones) are accessible to the view.
In short, no. This is because after the initial query, you are not left with a relational table or view, you are left with an array of activerecord objects. So any processing to be done after the initial query has to be in the format of ruby and activerecord, not sql.
I am trying to return a list of results, where the joined table has multiple values, but I only want one image value for each listing value.
The SQL is like this:
SELECT
Title, Comments, ThumbNailPath, thumbheight, thumbwidth
FROM
Listings as l INNER JOIN
Images as i ON l.id = i.ListingId
WHERE
(i.ImageSlot = 1)
My repository class looks something like this: (db.GetListings() is the stored procedure method I added to the methods section of the .dbml file)
private ListingModelDataContext db = new ListingModelDataContext();
public IQueryable FindAllListings()
{
//return all listings and first associated thumbnail
return db.GetListings();
}
When I try calling from stored procedure I get error
'System.Data.Linq.ISingleResult' to 'System.Linq.IQueryable'. An
explicit conversion exists (are you
missing a cast?)
I am looking for guidance on how I might either call that sql statement from a stored procedure or simply structure the linq to return that value.
My preference is to know how to write the LINQ statement. To clarify, I have a one to many relationship on the images table. (multiple images per listing) I only want to return the first image though on a search results page. So, for each listing return image value where imageSlot = 1.
I should get a list of rows showing the listing values joined to the image values. I get the correct results in SQL but not sure how to write it in linq or how to call the sproc correctly.
Thanks in advance and sorry if this is hard to read.
Are you trying to do soemthing like :
var result = (stored proc).Single()
or
var result = (stored proc).SingleOrDefault()
?? This would break if there are indeed multiple elements coming back - instead use the .First() or .FirstOrDefault() methods:
var result = (stored proc).FirstOfDefault();
returns the first entry from the stored proc, or null if the stored proc returns no values at all.
Marc