I'd like to get an average per type then join the aggregated table as a new column in the original table. Here's a visualization and code of what I'm attempting to do:
-- The original table --
ID | Cnt | Type
1 5 A
1 6 A
2 4 B
-- New Table --
ID | Cnt | Type | Avg
1 5 A 5.5
1 6 A 5.5
2 4 B 4.0
The code I have written thus far is the following:
select AVG(Cnt)
from old
group by(type)
right join on old
But, obviously it's not correct since a syntax error is raised. What would be the fix for this? I apologize in advance if my question is similar to an already existing one.
Use window functions:
select o.*, avg(cnt) over (partition by type)
from old o;
Related
I am trying to do an SQL query to count the total numbers of rows that contain each integer in a 'metric' column.
I.e. my data looks like:
RowName | Metric
Row 1 | 3
Row 2 | 3
Row 3 | 6
Row 4 | 6
And I want to find how many rows have a 'metric' value of 3, and how many have a value of 6:
Metric | Count
6 | 2
3 | 2
I have tried:
SELECT COUNT(Metric) FROM tablename GROUP BY Metric
But that returns an error. I know this is really simple and probably been answered many times before. As I am new to SQL I have tried searching, but probably don't quite know what I am searching for.
Thanks.
Below is for BigQuery Standard SQL
#standardSQL
SELECT Metric, COUNT(Metric) `Count`
FROM `project.dataset.your_table`
GROUP BY Metric
See it in action here
SELECT metric, [count]=COUNT(*)
FROM tablename
GROUP BY Metric
I have the following table structure.
ITEM TOTAL
----------- -----------------
ID | TITLE ID |ITEMID|VALUE
1 A 1 2 6
2 B 2 1 4
3 C 3 3 3
4 D 4 3 8
5 E 5 1 2
6 F 6 5 4
7 4 5
8 2 8
9 2 7
10 1 3
11 2 2
12 3 6
I am using Apache Derby DB. I need to perform the average calculation in SQL. I need to show the list of item IDs and their average total of the last 3 records.
That is, for ITEM.ID 1, I will go to TOTAL table and select the last 3 records of the rows which are associated with the ITEMID 1. And take average of them. In Derby database, I am able to do this for a given item ID but I cannot make it without giving a specific ID. Let me show you what I've done it.
SELECT ITEM.ID, AVG(VALUE) FROM ITEM, TOTAL WHERE TOTAL.ITEMID = ITEM.ID GROUP BY ITEM.ID
This SQL gives the average of all items in a list. But this calculates for all values of the total tables. I need last 3 records only. So I changed the SQL to this:
SELECT AVG(VALUE) FROM (SELECT ROW_NUMBER() OVER() AS ROWNUM, TOTAL.* FROM TOTAL WHERE ITEMID = 1) AS TR WHERE ROWNUM > (SELECT COUNT(ID) FROM TOTAL WHERE ITEMID = 1) - 3
This works if I supply the item ID 1 or 2 etc. But I cannot do this for all items without giving an item ID.
I tried to do the same thing in ORACLE using partition and it worked. But derby does not support partitioning. There is WINDOW but I could not make use of it.
Oracle one
SELECT ITEMID, AVG(VALUE) FROM(SELECT ITEMID, VALUE, COUNT(*) OVER (PARTITION BY ITEMID) QTY, ROW_NUMBER() OVER (PARTITION BY ITEMID ORDER BY ID) IDX FROM TOTAL ORDER BY ITEMID, ID) WHERE IDX > QTY -3 GROUP BY ITEMID ORDER BY ITEMID
I need to use derby DB for its portability.
The desired output is this
RESULT
-----------------
ITEMID | AVERAGE
1 (9/3)
2 (17/3)
3 (17/3)
4 (5/1)
5 (4/1)
6 NULL
As you have noticed, Derby's support for the SQL 2003 "OLAP Operations" support is incomplete.
There was some initial work (see https://wiki.apache.org/db-derby/OLAPOperations), but that work was only partially completed.
I don't believe anyone is currently working on adding more functionality to Derby in this area.
So yes, Derby has a row_number function, but no, Derby does not (currently) have partition by.
I have a Column of values in SQLite.
value
-----
1
2
3
4
5
For each value I would like to know how many of the other values are larger and display the result. E.g. For value 1 there are 4 entries that have higher values.
value | Count
-------------
1 | 4
2 | 3
3 | 2
4 | 1
5 | 0
I have tried nested select statements and using the Count(*) function but I do not seem to be able to extract the correct levels. Any suggestions would be much appreciated.
Many Thanks
You can do this with a correlated subquery in SQLite:
select value,
(select count(*) from t t2 where t2.value > t.value) as "count"
from t;
In most other databases, you would use a ranking function such as rank() or dense_rank(), but SQLite doesn't support these functions.
Consider the following table:
ID nonUniqueID value total
--------------------------
1 12345 5 x
2 12345 10 x
3 789 20 x
4 789 5 x
I need to make a query something like this (psuedo SQL), which will work within Access 2007:
UPDATE table
SET total = SUM(value)
WHERE nonUniqueID IS SAME;
The result should be as follows:
ID nonUniqueID value total
--------------------------
1 12345 5 15
2 12345 10 15
3 789 20 25
4 789 5 25
I've tried group bys, but I got odd results that quite frankly, I could not interpret. Does anybody know how I could achieve something like this?
Not sure if this works in Access or not, but give it a try:
update table t1
inner join (
select nonUniqueID, sum(value) as SumValue
from table
group by nonUniqueID
) t2 on t1.nonUniqueID = t2.nonUniqueID
set t1.total = t2.SumValue
Update: Based on this question, it looks like it is not going to work. But give it a shot! If it doesn't, you can use the approach suggested in that question.
Another possible option:
update t
set total = (select SUM(value) from table where nonUniqueID = t.nonUniqueID)
from table t
Image you are creating a DB schema for a threaded discussion board. Is there an efficient way to select a properly sorted list for a given thread? The code I have written works but does not sort the way I would like it too.
Let's say you have this data:
ID | ParentID
-----------------
1 | null
2 | 1
3 | 2
4 | 1
5 | 3
So the structure is supposed to look like this:
1
|- 2
| |- 3
| | |- 5
|- 4
Ideally, in the code, we want the result set to appear in the following order: 1, 2, 3, 5, 4
PROBLEM: With the CTE I wrote it is actually being returned as: 1, 2, 4, 3, 5
I know this would be easy to group/order by using LINQ but I am reluctant to do this in memory. It seems like the best solution at this point though...
Here is the CTE I am currently using:
with Replies as (
select c.CommentID, c.ParentCommentID 1 as Level
from Comment c
where ParentCommentID is null and CommentID = #ParentCommentID
union all
select c.CommentID, c.ParentCommentID, r.Level + 1 as Level
from Comment c
inner join Replies r on c.ParentCommentID = r.CommentID
)
select * from Replies
Any help would be appreciated; Thanks!
I'm new to SQL and had not heard about hierarchyid datatype before. After reading about it from this comment I decided I may want to incorporate this into my design. I will experiment with this tonight and post more information if I have success.
Update
Returned result from my sample data, using dance2die's suggestion:
ID | ParentID | Level | DenseRank
-------------------------------------
15 NULL 1 1
20 15 2 1
21 20 3 1
17 22 3 1
22 15 2 2
31 15 2 3
32 15 2 4
33 15 2 5
34 15 2 6
35 15 2 7
36 15 2 8
I am sure that you will love this.
I recently find out about Dense_Rank() function, which is for "ranking within the partition of a result set" according to MSDN
Check out the code below and how "CommentID" is sorted.
As far as I understand, you are trying to partition your result set by ParentCommentID.
Pay attention to "denserank" column.
with Replies (CommentID, ParentCommentID, Level) as
(
select c.CommentID, c.ParentCommentID, 1 as Level
from Comment c
where ParentCommentID is null and CommentID = 1
union all
select c.CommentID, c.ParentCommentID, r.Level + 1 as Level
from Comment c
inner join Replies r on c.ParentCommentID = r.CommentID
)
select *,
denserank = dense_rank() over (partition by ParentCommentID order by CommentID)
from Replies
order by denserank
Result below
You have to use hierarchyid (sql2008 only) or a bunch of string (or byte) concatenation.
Hmmmm - I am not sure if your structure is the best suited for this problem. Off the top of my head I cannot think of anyway to sort the data as you want it within the above query.
The best I can think of is if you have a parent table that ties your comments together (eg. a topic table). If you do you should be able to simply join your replies onto that (you will need to include the correct column obviously), and then you can sort by the topicID, Level to get the sort order you are after (or whatever other info on the topic table represents a good value for sorting).
Consider storing the entire hierarchy (with triggers to update it if it changes ) in a field.
This field in your example would have:
1
1.2
1.2.3
1.2.5
1.4
then you just have to sort on that field, try this and see:
create table #temp (test varchar (10))
insert into #temp (test)
select '1'
union select '1.2'
union select '1.2.3'
union select '1.2.5'
union select '1.4'
select * from #temp order by test asc