I started code rails recently and I need to figure out this problem.
%td
= Ahoy::Event.where(name: "viewed_brochure").where_properties(brochure_id: brochure.id).select(:session_id).uniq
This should find number of distinct values of session_id in properties field but it doesn't work.
This line returns these and similar errors
#<Ahoy::Event::ActiveRecord_Relation:0x007f52d9325130>
#<Ahoy::Event::ActiveRecord_Relation:0x007f52d9466508>
%td
= Ahoy::Event.select { |event| event.properties['session_id'] }.uniq.count
I tried this line but this time returns number of rows in table
You can try to group by jsonb key, in your case properties['session_id']
Ahoy::Event.group("properties -> 'session_id'").count
This will return the counts on which you can apply .size or you could do distinct.
Thank u so much #Anton I modify your solution and finally it works fine.
Here is the solution
%td
= Ahoy::Event.where_properties(brochure_id: brochure.id).group("properties -> 'session_id'").count.size
I'm trying to learn about SQL injections and have tried to implement these, but when I put this code in my controller:
params[:username] = "johndoe') OR admin = 't' --"
#user_query = User.find(:first, :conditions => "username = '#{params[:username]}'")
I get the following error:
Couldn't find all Users with 'id': (first, {:conditions=>"username = 'johndoe') OR admin = 't' --'"}) (found 0 results, but was looking for 2)
I have created a User Model with the username "johndoe", but I am still getting no proper response. BTW I am using Rails 4.
You're using an ancient Rails syntax. Don't use
find(:first, :condition => <condition>) ...
Instead use
User.where(<condtion>).first
find accepts a list of IDs to lookup records for. You're giving it an ID of :first and an ID of condition: ..., which aren't going to match any records.
User.where(attr1: value, attr2: value2)
or for single items
User.find_by(attr1: value, attr2: value)
Bear in mind that while doing all this, it would be valuable to check what the actual sql statement is by adding "to_sql" to the end of the query method (From what I remember, find_by just does a LIMIT by 1)
I need to perform data smoothing using averaging, with a non-standard group_by variable that is created on-the-fly. My model consists of two tables:
class WthrStn(models.Model):
name=models.CharField(max_length=64, error_messages=MOD_ERR_MSGS)
owner_email=models.EmailField('Contact email')
location_city=models.CharField(max_length=32, blank=True)
location_state=models.CharField(max_length=32, blank=True)
...
class WthrData(models.Model):
stn=models.ForeignKey(WthrStn)
date=models.DateField()
time=models.TimeField()
temptr_out=models.DecimalField(max_digits=5, decimal_places=2)
temptr_in=models.DecimalField(max_digits=5, decimal_places=2)
class Meta:
ordering = ['-date','-time']
unique_together = (("date", "time", "stn"),)
The data in WthrData table are entered from an xml file in variable time increments, currently 15 or 30 minutes, but that could vary and change over time. There are >20000 records in that table. I want to provide an option to display the data smoothed to variable time units, e.g. 30 minutes, 1, 2 or N hours (60, 120, 180, etc minutes)
I am using SQLIte3 as the DB engine. I tested the following sql, which proved quite adequate to perform the smoothing in 'bins' of N-minutes duration:
select id, date, time, 24*60*julianday(datetime(date || time))/N jsec, avg(temptr_out)
as temptr_out, avg(temptr_in) as temptr_in, avg(barom_mmhg) as barom_mmhg,
avg(wind_mph) as wind_mph, avg(wind_dir) as wind_dir, avg(humid_pct) as humid_pct,
avg(rain_in) as rain_in, avg(rain_rate) as rain_rate,
datetime(avg(julianday(datetime(date || time)))) as avg_date from wthr_wthrdata where
stn_id=19 group by round(jsec,0) order by stn_id,date,time;
Note I create an output variable 'jsec' using the SQLite3 function 'julianday', which returns number of days in the integer part and fraction of day in the decimal part. So, multiplying by 24*60 gives me number of minutes. Dividing by N-minute resolution gives me a nice 'group by' variable, compensating for varying time increments of the raw data.
How can I implement this in Django? I have tried the objects.raw(), but that returns a RawQuerySet, not a QuerySet to the view, so I get error messages from the html template:
</p>
Number of data entries: {{ valid_form|length }}
</p>
I have tried using a standard Query, with code like this:
wthrdta=WthrData.objects.all()
wthrdta.extra(select={'jsec':'24*60*julianday(datetime(date || time))/{}'.format(n)})
wthrdta.extra(select = {'temptr_out':'avg(temptr_out)',
'temptr_in':'avg(temptr_in)',
'barom_mmhg':'avg(barom_mmhg)',
'wind_mph':'avg(wind_mph)',
'wind_dir':'avg(wind_dir)',
'humid_pct':'avg(humid_pct)',
'rain_in':'avg(rain_in)',
'rain_sum_in':'sum(rain_in)',
'rain_rate':'avg(rain_rate)',
'avg_date':'datetime(avg(julianday(datetime(date || time))))'})
Note that here I use the sql-avg functions instead of using the django aggregate() or annotate(). This seems to generate correct sql code, but I cant seem to get the group_by set properly to my jsec data that is created at the top.
Any suggestions for how to approach this? All I really need is to have the QuerySet.raw() method return a QuerySet, or something that can be converted to a QuerySet instead of RawQuerySet. I can not find an easy way to do that.
The answer to this turns out to be really simple, using a hint I found from
[https://gist.github.com/carymrobbins/8477219][1]
though I modified his code slightly. To return a QuerySet from a RawQuerySet, all I did was add to my models.py file, right above the WthrData class definition:
class MyManager(models.Manager):
def raw_as_qs(self, raw_query, params=()):
"""Execute a raw query and return a QuerySet. The first column in the
result set must be the id field for the model.
:type raw_query: str | unicode
:type params: tuple[T] | dict[str | unicode, T]
:rtype: django.db.models.query.QuerySet
"""
cursor = connection.cursor()
try:
cursor.execute(raw_query, params)
return self.filter(id__in=(x[0] for x in cursor))
finally:
cursor.close()
Then in my class definition for WthrData:
class WthrData(models.Model):
objects=MyManager()
......
and later in the WthrData class:
def get_smoothWthrData(stn_id,n):
sqlcode='select id, date, time, 24*60*julianday(datetime(date || time))/%s jsec, avg(temptr_out) as temptr_out, avg(temptr_in) as temptr_in, avg(barom_mmhg) as barom_mmhg, avg(wind_mph) as wind_mph, avg(wind_dir) as wind_dir, avg(humid_pct) as humid_pct, avg(rain_in) as rain_in, avg(rain_rate) as rain_rate, datetime(avg(julianday(datetime(date || time)))) as avg_date from wthr_wthrdata where stn_id=%s group by round(jsec,0) order by stn_id,date,time;'
return WthrData.objects.raw_as_qs(sqlcode,[n,stn_id]);
This allows me to grab results from the highly populated WthrData table smoothed over time increments, and the results come back as a QuerySet instead of RawQuerySet
I currently have a .find method in one of my rails controller actions - the relevant part is:
.find(:all, :select => 'last_name as id, last_name as name')
I am getting some odd behaviour trying to alias the last_name column as id - if I alias it as anything else, it works fine (i can do last_name as xyz and it outputs the last name in a column called xyz, but as I am using this to populate a drop-down where I need to have the name in the id column, i need it to be called 'id').
I should point out that it does output an id column, but it is always "id":0.
Could anyone shed any light on what I need to do to get this column aliased as 'id'?
Thanks!
I'm not sure of how you can do this in a Rails query statement. Rails is going to try and take over the id column, casting the value returned by the database as id with the type of column that id is (presumably integer). That's why your id column keeps getting set to 0, because "string".to_i #=> 0
However, there is a way to do it, once you have the results back.
Since you have the question tagged as Rails 3, it is preferable to use the new ActiveRelation syntax. You can do the following:
# First, get the results from the query, then loop through all of them.
Customer.select("last_name as 'ln', last_name as 'name'").all.collect do |c|
# The first step of the loop is to get the attributes into a hash form
h = c.attributes
# The next step is to create an "id" key in the hash.
# The Hash#delete method deletes the key/value pair at the key specified and returns the value.
# We'll take that returned value and assign it to the just created "id" key.
h["id"] = h.delete("ln")
# And we have to call out the hash to ensure that it's the returned value from the collect.
h
end
That will get you a hash with the id value as the text string value last_name and a name value as the same.
Hope that helps!
You shouldn't need to setup aliases in the finder SQL just to populate a drop-down. Instead simply use the last_name value for the value attribute (as well as the display text).
Eg if you're using the collection_select helper:
<%= f.collection_select :attribute_id, #collection, :last_name, :last_name %>
I wanted to know how we could store the result of my select query on a variable.
#ppt2 = Ppt.select('slide_name').where('id=?',4)
#ppt1 = Ppt.update_all({:time2=>#ppt2},['id like ?','1'])
Here, slide_name and time2 are both text attributes of the same table ppt.
What happens on the above execution is that the time2 field in id=1 gets the value "#ppt2" whereas I want it to get the value of slide_name from id=4 which does not get stored in #ppt1.
In other words, how do I store the value of the select query in #ppt2 so that it can be used in the next line?
Any help is appreciated.
Call the slide_name method on your first result.
#ppt2 = Ppt.select('slide_name').find(4).slide_name