sum interview questions
Top sum frequently asked interview questions
Say I have a simple function in MySQL:
$query="SELECT SUM(Column 1) from Table WHERE Column 2='Test'";
If no entries in Column 2 contain the text 'Test' then this function returns NULL, when I would like it to return 0. I'm aware that a similar question has been asked a few times here, but I haven't been able to adapt the answers to my purposes, so I'd be grateful for some help to get this sorted.
Thanks,
Nick
Source: (StackOverflow)
from i in Db.Items
select new VotedItem
{
ItemId = i.ItemId,
Points = (from v in Db.Votes
where b.ItemId == v.ItemId
select v.Points).Sum()
}
I got this query, however it fails if no votes are found with exception:
The null value cannot be assigned to a member with type System.Int32 which is a non-nullable value type.
I assume its because sum returns an int and not a nullable int, giving sum a int? as input only give the same error, probably cause sum only workes on ints.
Any good workaround for this?
Source: (StackOverflow)
let's say that I have a table called
Items (ID int, Done int, Total int)
I can do it by two queries:
int total = m.Items.Sum(p=>p.Total)
int done = m.Items.Sum(p=>p.Done)
But I'd like to do it in one query, something like this:
var x = from p in m.Items select new { Sum(p.Total), Sum(p.Done)};
Surely there is a way to call aggregate functions from LINQ syntax...?
Source: (StackOverflow)
I have the following two lists:
first = [1,2,3,4,5]
second = [6,7,8,9,10]
Now I want to add items of both lists into a new list.
output should be
three = [7,9,11,13,15]
Source: (StackOverflow)
I'm having a problem finding the sum of all of the integers in an array in java. Cannot find any useful method in the Math class for this.
Source: (StackOverflow)
I have a data frame with several columns; some numeric and some character. How to compute the sum of a specific column? I’ve googled for this and I see numerous functions (sum
, cumsum
, rowsum
, rowSums
, colSums
, aggregate
, apply
) but I can’t make sense of it all.
For example suppose I have a data frame people
with the following columns
Name Height Weight
Mary 65 110
John 70 200
Jane 64 115
…
How do I get the sum of all the weights?
Source: (StackOverflow)
I reckon this will be quite trivial but I can't work out how to do it. I have a List<int>
and I want to sum a range of the numbers.
Say my list is:
var list = new List<int>()
{
1, 2, 3, 4
};
How would I get the sum of the first 3 objects? The result being 6. I tried using Enumerable.Range
but couldn't get it to work, not sure if that's the best way of going about it.
Without doing:
int sum = list[0] + list[1] + list[2];
Source: (StackOverflow)
I want to get N random numbers that the sum of them is a value.
For example, let's suppose I want 5 random numbers that their sum is 1
Then, a valid possibility is:
0.2 0.2 0.2 0.2 0.2
Other possibility is:
0.8 0.1 0.03 0.03 0.04
And so on. I need this for the creation of the matrix of belongings of the Fuzzy C-means.
Source: (StackOverflow)
I'm just started to read up on LINQ and I want to start incorporating it into my code. I know how to compute the sum of a DataTable's column by either "Foreach"-ing through the rows or by doing a compute.sum on the specific column. How do I do the equivalent with LINQ to DataSet?
Source: (StackOverflow)
I have an array of integers.
For example:
array = [123,321,12389]
Is there any nice way to get the sum of them?
I know, that
sum = 0
array.each { |a| sum+=a }
would work.
Source: (StackOverflow)
I have a list of objects. One property of the individual object entry is amount. How do I get the sum of amount?
If my list was of type double I may be able to do something like this:
double total = myList.Sum();
However I want to something similar to this, yet this syntax is incorrect.
double total = myList.amount.Sum();
How should I go about accomplishing this? I would love to use the Sum function if possible instead of looping through and calculating the value.
Source: (StackOverflow)
I have a collection of boxes with the properties weight, volume and owner.
I want to use LINQ to get a summarized list (by owner) of the box information
e.g.
**Owner, Boxes, Total Weight, Total Volume**
Jim, 5, 1430.00, 3.65
George, 2, 37.50, 1.22
Can someone show me how to do this with Lambda expressions?
Source: (StackOverflow)
I'm new to Python. Let's say I have a dictionary in which the keys map to integers like:
d = {'key1':1,'key2':14,'key3':47}
Is there a syntactically minimalistic way to return the sum of the values in d--i.e. 62 in this case.
Thanks
Source: (StackOverflow)
I'm trying to update a field in the database to the sum of its joined values:
UPDATE P
SET extrasPrice = SUM(E.price)
FROM dbo.BookingPitchExtras AS E
INNER JOIN dbo.BookingPitches AS P ON E.pitchID = P.ID
AND P.bookingID = 1
WHERE E.[required] = 1
When I run this I get the following error:
"An aggregate may not appear in the set list of an UPDATE statement."
Any ideas?
Source: (StackOverflow)
I understand that in order to sum array elements in Ruby one can use the inject method, i.e.
array = [1,2,3,4,5];
puts array.inject(0, &:+)
But how do I sum the properties of objects within an object array e.g.?
There's an array of objects and each object has a property "cash" for example. So I want to sum their cash balances into one total. Something like...
array.cash.inject(0, &:+) # (but this doesn't work)
I realise I could probably make a new array composed only of the property cash and sum this, but I'm looking for a cleaner method if possible!
Source: (StackOverflow)