Getting average low and high bids in SQL - sql

I am pretty new to SQL and am working with a (what I expected to be easy) little bidding tool.
I am trying to compute average lows and highs from the same column. I have managed to figure out how to use SQL's MIN, MAX, AVG functions, but how would I go about averaging MIN and MAX?
This is the query I am using:
$query = $pdo->prepare("SELECT AVG(bid),MIN(bid),MAX(bid) FROM bidding WHERE bid_id=:bid_id GROUP BY bid_id");


Try the following query to accomplish task
SELECT ((max(bid)+min(bid))/2) as average FROM bidding WHERE bid_id=:bid_id GROUP BY bid_id
Because the predefined avg function takes only one argument that may be column from table or single value. So you have to find the average of the min and max value of bid like above


As You are saying you need to find out the Min of Avg and Max of Avg,
Now what you are doing is group on one column this means Avg(Bid) will return only one value. And the thing that you are doing will make sense only if it is done with two column,
For example you wanna know the min of Averages per day. You need to identify one more column on which base you want to find out max and min of Avg. See in my example i am using Date as second column. the query will go like.
Select Max(MAx_Bid),Min(Min_Bid),Min(Avg_Bid),Max(Avg_Bid) FROM
(SELECT AVG(bid) Avg_Bid,MIN(bid) Mix_Bid,MAX(bid) max_bid FROM bidding WHERE bid_id=:bid_id GROUP BY bid_id,Days_Date(Dummy column))A

Related

How to get the Average of a Row After Getting Count?

I am trying to use an aggregate function to get the average(count( of a row in SQL Server. However, I continue to get this message:
"Cannot perform an aggregate function on an expression containing an aggregate or a subquery."
In the first picture is the table, in the second picture is the table with the counts for each officer_id, I am trying to find the average amount of calls per officer and cannot seem to find the right SQL query to do it.
The query I thought may work is:
SELECT AVG(COUNT(officer_id))
FROM crime_officers
ORDER BY officer_id;
But this is where I get the aggregate error. Does anyone have any recommendations?
UPDATED table with this query
SELECT officer_id, COUNT(crime_id)
FROM crime_officers
GROUP BY officer_id;
Original table: crime_officers

If I understand correctly, this query provides the average number of crimes per officer. A single value, which is equal to the total number of crimes divided between all officers.
SELECT COUNT(*)*1.0/COUNT(distinct officer_id) as 'Average Crimes per Officer'
FROM crime_officers;

Creating custom timestamp buckets bigquery

I have an hourly (timestamp) dataset of events from the past month.
I would like to check the performance of events that occurred between certain hours, group them together and average the results.
For example: AVG income of the hours 23:00-02:00 per user:
So if I have this data set below. I'd like to summarise the coloured rows and then average them (the result should be 218).
I tried NTILE but it couldn't divide the data properly, ignoring the irrelevant hours.
Is there a good way to create these custom buckets using SQL?
dataset

From description not exactly sure how you want to aggregate. If you provide an example dataset can update answer.
However you can easily achieve this with an AVG and IF statement.
AVG(IF(EXTRACT(HOUR FROM timestamp_field) BETWEEN 0 AND 4, value, NULL) as avg_value
Using the above you can then group by either day or month to get the aggregation level you want.

How to calculate the avg time a tool stays on hold? oracle sql developer

Im trying to calculate the average time a tool stays on loan. The time a tool stays on loan is the number of days between loan_status_change_date and tool_out_date (table columns). the date type of these 2 columns is ex: 01-SEP-17
whats the best way to approach this?

We can do arithmetic with Oracle dates. It's not clear from the column names which one is the start of the loan and which the end; in the following example I've assumed loan_status_change is when the tool is returned.
select tool
, avg(loan_status_change - tool_out_date) as avg_loan_days
from your_table
group by tool
/
The AVG() function is an aggregate function, so it handles the /ns for us. The substraction is to calculate the length of a particular loan, which is the value you want to average. The result of that substraction already is a number of days, so no further transformation is necessary. If your columns have a time element then the result might not be an integer.

SQL GROUPING SETS averages with multiple many-to-many dimensions

I have a table of data with the following:
User,Platform,Dt,Activity_Flag,Total_Purchases
1,iOS,05/05/2016,1,1
1,Android,05/05/2016,1,2
2,iOS,05/05/2016,1,0
2,Android,05/05/2016,1,2
3,iOS,05/05/2016,1,1
3,Android,06/05/2016,1,3
1,iOS,06/05/2016,1,2
4,Android,06/05/2016,1,2
1,Android,06/05/2016,1,0
3,iOS,07/05/2016,1,2
2,iOS,08/05/2016,1,0
I want to do a GROUPING SETS (Platform,Dt,(Platform,Dt),()) aggregation to be able to find for each combination of Platform and Dt the following:
Total Purchases
Total Unique Users
Average Purchases per User per Day
The first two are simple as these can be achieved via a sum(Total_Purchases) and count(distinct user) respectively.
The problem I have is with the last metric. The result set should look like this but I don't know how to get the last column to be calculated correctly:
Platform,Dt,Total_Purchases,Total_Unique_Users,Average_Purchases_Per_User_Per_Day
Android,05/05/2016,4,2,2.0
iOS,05/05/2016,2,3,0.7
Android,06/05/2016,5,3,1.7
iOS,06/05/2016,2,1,2.0
iOS,07/05/2016,2,1,2.0
iOS,08/05/2016,0,1,0.0
,05/05/2016,6,3,2.0
,06/05/2016,7,3,2.3
,07/05/2016,1,1,1.0
,08/05/2016,1,1,1.0
Android,,9,4,1.8
iOS,,6,3,1.2
,,15,4,1.6
For the first ten rows we see that getting the Average purchase per user per day is a simple division of the first two columns as the dimension in these rows represent a single date only. But when we look at the final 3 rows we see that the division is not the way to achieve the desired result. This is because it needs to take an average for each day in turn to get the overall per day amount.
If this isn't clear please let me know and I'll be happy to explain better. This is my first post on this site!

How does the aggregation function work with group by

I do not understand the following (returns numbers of comments for articles with the newest ones dates):
SELECT `id_comment`,COUNT(*) AS `number`, MAX(`date`) AS `newest`
FROM `page_comments`
WHERE TO_DAYS( NOW() )-TO_DAYS(`date`) < 90
GROUP BY `id_comment`
ORDER BY `count` DESC,`newest` DESC
I dont understand how come that the MAX function will not return the MAX value of all the page_comments table? That it automatically takes only the max for the given group. When using MAX, I would expect it to return the highest value of the column. I dont understand how it works together with groupig.

You described the behavior yourself quite correctly already: it automatically takes only the max for the given group.
If you group, you do it (per usual) on every column in the result set, that is not aggregated (not using COUNT, SUM, MIN, MAX...)
That way you get distinct values for all non aggregated columns and the aggregated ones will yield a result that only takes the 'current' group into account.

I am just explaining it to the ground.
MAX() - An aggregate function(Works over the group of data).
If ""group by"" clause is NOT specified, the database implicitly groups the data(column specified) considering the entire result set as group.
If specified, it just groups the data(column) in the group logic specified.

It all boils down to analysis order:
FROM
ON
OUTER
WHERE
GROUP BY
CUBE | ROLLUP
HAVING
SELECT
DISTINCT
10 ORDER BY
TOP
so you first have the from clause
Then you cut the relevant rows via where ( so here your sentence : *I don't understand how come that the MAX function will not return the MAX value of all the page_comments* --fails)
then group it
Then you select it.
The max and aggregate functions apply on the data which is already filtered!