I have 2 tables - an Account table and a Users table. Each account can have multiple users. I have a scenario where I want to execute a single query/join against these two tables, but I want all the Account data (Account.*) and only the first set of user data (specifically their name).
Instead of doing a "min" or "max" on my aggregated group, I wanted to do a "first". But, apparently, there is no "First" aggregate function in TSQL.
Any suggestions on how to go about getting this query? Obviously, it is easy to get the cartesian product of Account x Users:
SELECT User.Name, Account.* FROM Account, User
WHERE Account.ID = User.Account_ID
But how might I got about only getting the first user from the product based on the order of their User.ID ?
Rather than grouping, go about it like this...
select
*
from account a
join (
select
account_id,
row_number() over (order by account_id, id) -
rank() over (order by account_id) as row_num from user
) first on first.account_id = a.id and first.row_num = 0
I know my answer is a bit late, but that might help others. There is a way to achieve a First() and Last() in SQL Server, and here it is :
Stuff(Min(Convert(Varchar, DATE_FIELD, 126) + Convert(Varchar, DESIRED_FIELD)), 1, 23, '')
Use Min() for First() and Max() for Last(). The DATE_FIELD should be the date that determines if it is the first or last record. The DESIRED_FIELD is the field you want the first or the last value. What it does is :
Add the date in ISO format at the start of the string (23 characters long)
Append the DESIRED_FIELD to that string
Get the MIN/MAX value for that field (since it start with the date, you will get the first or last record)
Stuff that concatened string to remove the first 23 characters (the date part)
Here you go!
EDIT: I got problems with the first formula : when the DATE_FIELD has .000 as milliseconds, SQL Server returns the date as string with NO milliseconds at all, thus removing the first 4 characters from the DESIRED_FIELD. I simply changed the format to "20" (without milliseconds) and it works all great. The only downside is if you have two fields that were created at the same seconds, the sort can possibly be messy... in which cas you can revert to "126" for the format.
Stuff(Max(Convert(Varchar, DATE_FIELD, 20) + Convert(Varchar, DESIRED_FIELD)), 1, 19, '')
EDIT 2 : My original intent was to return the last (or first) NON NULL row. I got asked how to return the last or first row, wether it be null or not. Simply add a ISNULL to the DESIRED_FIELD. When you concatenate two strings with a + operator, when one of them is NULL, the result is NULL. So use the following :
Stuff(Max(Convert(Varchar, DATE_FIELD, 20) + IsNull(Convert(Varchar, DESIRED_FIELD), '')), 1, 19, '')
Select *
From Accounts a
Left Join (
Select u.*,
row_number() over (Partition By u.AccountKey Order By u.UserKey) as Ranking
From Users u
) as UsersRanked
on UsersRanked.AccountKey = a.AccountKey and UsersRanked.Ranking = 1
This can be simplified by using the Partition By clause. In the above, if an account has three users, then the subquery numbers them 1,2, and 3, and for a different AccountKey, it will reset the numnbering. This means for each unique AccountKey, there will always be a 1, and potentially 2,3,4, etc.
Thus you filter on Ranking=1 to grab the first from each group.
This will give you one row per account, and if there is at least one user for that account, then it will give you the user with the lowest key(because I use a left join, you will always get an account listing even if no user exists). Replace Order By u.UserKey with another field if you prefer that the first user be chosen alphabetically or some other criteria.
I've benchmarked all the methods, the simpelest and fastest method to achieve this is by using outer/cross apply
SELECT u.Name, Account.* FROM Account
OUTER APPLY (SELECT TOP 1 * FROM User WHERE Account.ID = Account_ID ) as u
CROSS APPLY works just like INNER JOIN and fetches the rows where both tables are related, while OUTER APPLY works like LEFT OUTER JOIN and fetches all rows from the left table (Account here)
You can use OUTER APPLY, see documentation.
SELECT User1.Name, Account.* FROM Account
OUTER APPLY
(SELECT TOP 1 Name
FROM [User]
WHERE Account.ID = [User].Account_ID
ORDER BY Name ASC) User1
SELECT (SELECT TOP 1 Name
FROM User
WHERE Account_ID = a.AccountID
ORDER BY UserID) [Name],
a.*
FROM Account a
The STUFF response from Dominic Goulet is slick. But, if your DATE_FIELD is SMALLDATETIME (instead of DATETIME), then the ISO 8601 length will be 19 instead of 23 (because SMALLDATETIME has no milliseconds) - so adjust the STUFF parameter accordingly or the return value from the STUFF function will be incorrect (missing the first four characters).
First and Last do not exist in Sql Server 2005 or 2008, but in Sql Server 2012 there is a First_Value, Last_Value function. I tried to implement the aggregate First and Last for Sql Server 2005 and came to the obstacle that sql server does guarantee the calculation of the aggregate in a defined order. (See attribute SqlUserDefinedAggregateAttribute.IsInvariantToOrder Property, which is not implemented.) This might be because the query analyser tries to execute the calculation of the aggregate on multiple threads and combine the results, which speeds up the execution, but does not guarantee an order in which elements are aggregated.
Define "First". What you think of as first is a coincidence that normally has to do with clustered index order but should not be relied on (you can contrive examples that break it).
You are right not to use MAX() or MIN(). While tempting, consider the scenario where you the first name and last name are in separate fields. You might get names from different records.
Since it sounds like all your really care is that you get exactly one arbitrary record for each group, what you can do is just MIN or MAX an ID field for that record, and then join the table into the query on that ID.
There are a number of ways of doing this, here a a quick and dirty one.
Select (SELECT TOP 1 U.Name FROM Users U WHERE U.Account_ID = A.ID) AS "Name,
A.*
FROM Account A
(Slightly Off-Topic, but) I often run aggregate queries to list exception summaries, and then I want to know WHY a customer is in the results, so use MIN and MAX to give 2 semi-random samples that I can look at in details e.g.
SELECT Customer.Id, COUNT(*) AS ProblemCount
, MIN(Invoice.Id) AS MinInv, MAX(Invoice.Id) AS MaxInv
FROM Customer
INNER JOIN Invoice on Invoice.CustomerId = Customer.Id
WHERE Invoice.SomethingHasGoneWrong=1
GROUP BY Customer.Id
Create and join with a subselect 'FirstUser' that returns the first user for each account
SELECT User.Name, Account.*
FROM Account, User,
(select min(user.id) id,account_id from User group by user.account_id) as firstUser
WHERE Account.ID = User.Account_ID
and User.id = firstUser.id and Account.ID = firstUser.account_id
Related
In AWS Timestream I am trying to get the average heart rate for the first month since we have received heart rate samples for a specific user and the average for the last week. I'm having trouble with the query to get the first month part. When I try to use MIN(time) in the where clause I get the error: WHERE clause cannot contain aggregations, window functions or grouping operations.
SELECT * FROM "DATABASE"."TABLE"
WHERE measure_name = 'heart_rate' AND time < min(time) + 30
If I add it as a column and try to query on the column, I get the error: Column 'first_sample_time' does not exist
SELECT MIN(time) AS first_sample_time FROM "DATABASE"."TABLE"
WHERE measure_name = 'heart_rate' AND time > first_sample_time
Also if I try to add to MIN(time) I get the error: line 1:18: '+' cannot be applied to timestamp, integer
SELECT MIN(time) + 30 AS first_sample_time FROM "DATABASE"."TABLE"
Here is what I finally came up with but I'm wondering if there is a better way to do it?
WITH first_month AS (
SELECT
Min(time) AS creation_date,
From_milliseconds(
To_milliseconds(
Min(time)
) + 2628000000
) AS end_of_first_month,
USER
FROM
"DATABASE"."TABLE"
WHERE
USER = 'xxx'
AND measure_name = 'heart_rate'
GROUP BY
USER
),
first_month_avg AS (
SELECT
Avg(hm.measure_value :: DOUBLE) AS first_month_average,
fm.USER
FROM
"DATABASE"."TABLE" hm
JOIN first_month fm ON hm.USER = fm.USER
WHERE
measure_name = 'heart_rate'
AND hm.time BETWEEN fm.creation_date
AND fm.end_of_first_month
GROUP BY
fm.USER
),
last_week_avg AS (
SELECT
Avg(measure_value :: DOUBLE) AS last_week_average,
USER
FROM
"DATABASE"."TABLE"
WHERE
measure_name = 'heart_rate'
AND time > ago(14d)
AND USER = 'xxx'
GROUP BY
USER
)
SELECT
lwa.last_week_average,
fma.first_month_average,
lwa.USER
FROM
first_month_avg fma
JOIN last_week_avg lwa ON fma.USER = lwa.USER
Is there a better or more efficient way to do this?
I can see you've run into a few challenges along the way to your solution, and hopefully I can clear these up for you and also propose a cleaner way of reaching your solution.
Filtering on aggregates
As you've experienced first hand, SQL doesn't allow aggregates in the where statement, and you also cannot filter on new columns you've created in the select statement, such as aggregates or case statements, as those columns/results are not present in the table you're querying.
Fortunately there are ways around this, such as:
Making your main query a subquery, and then filtering on the result of that query, like below
Select * from (select *,count(that_good_stuff) as total_good_stuff from tasty_table group by 1,2,3) where total_good_stuff > 69
This works because the aggregate column (count) is no longer an aggregate at the time it's called in the where statement, it's in the result of the subquery.
Having clause
If a subquery isn't your cup of tea, you can use the having clause straight after your group by statement, which acts like a where statement except exclusively for handling aggregates.
This is better than resorting to a subquery in most cases, as it's more readable and I believe more efficient.
select *,count(that_good_stuff) as total_good_stuff from tasty_table group by 1,2,3 having total_good_stuff > 69
Finally, window statements are fantastic...they've really helped condense many queries I've made in the past by removing the need for subqueries/ctes. If you could share some example raw data (remove any pii of course) I'd be happy to share an example for your use case.
Nevertheless, hope this helps!
Tom
I need to figure out how to eliminate older revisions from my query's results, my database stores orders as 'Q000000' and revisions have an appended '-number'. My query currently is as follows:
SELECT DISTINCT Estimate.EstimateNo
FROM Estimate
INNER JOIN EstimateDetails ON EstimateDetails.EstimateID = Estimate.EstimateID
INNER JOIN EstimateDoorList ON EstimateDoorList.ItemSpecID = EstimateDetails.ItemSpecID
WHERE (Estimate.SalesRepID = '67' OR Estimate.SalesRepID = '61') AND Estimate.EntryDate >= '2017-01-01 00:00:00.000' AND EstimateDoorList.SlabSpecies LIKE '%MDF%'
ORDER BY Estimate.EstimateNo
So for instance, the results would include:
Q120455-10
Q120445-11
Q121675-2
Q122361-1
Q123456
Q123456-1
From this, I need to eliminate 'Q120455-10' because of the presence of '-11' for that order, and 'Q123456' because of the presence of the '-1' revision. I'm struggling greatly with figuring out how to do this, my immediate thought was to use case statements but I'm not sure what is the best way to implement them and how to filter. Thank you in advance, let me know if any more information is needed.
First you have to parse your EstimateNo column into sequence number and revision number using CHARINDEX and SUBSTRING (or STRING_SPLIT in newer versions) and CAST/CONVERT the revision to a numeric type
SELECT
SUBSTRING(Estimate.EstimateNo,0,CHARINDEX('-',Estimate.EstimateNo)) as [EstimateNo],
CAST(SUBSTRING(Estimate.EstimateNo,CHARINDEX('-',Estimate.EstimateNo)+1, LEN(Estimate.EstimateNo)-CHARINDEX('-',Estimate.EstimateNo)+1) as INT) as [EstimateRevision]
FROM
...
You can then use
APPLY - to select TOP 1 row that matches the EstimateNo or
Window function such as ROW_NUMBER to select only records with row number of 1
For example, using a ROW_NUMBER would look something like below:
SELECT
ROW_NUMBER() OVER(PARTITION BY EstimateNo ORDER BY EstimateRevision DESC) AS "LastRevisionForEstimate",
-- rest of the needed columns
FROM
(
-- query above goes here
)
You can then wrap the query above in a simple select with a where predicate filtering out a specific value of LastRevisionForEstimate, for instance
SELECT --needed columns
FROM -- result set above
WHERE LastRevisionForEstimate = 1
Please note that this is to a certain extent, pseudocode, as I do not have your schema and cannot test the query
If you dislike the nested selects, check out the Common Table Expressions
I'm using Access (I normally use SQL Server) for a little job, and I'm getting "enter parameter value" for Night.NightId in the statement below that has a subquery within a subquery. I expect it would work if I wasn't nesting it two levels deep, but I can't think of a way around it (query ideas welcome).
The scenario is pretty simple, there's a Night table with a one-to-many relationship to a Score table - each night normally has 10 scores. Each score has a bit field IsDouble which is normally true for two of the scores.
I want to list all of the nights, with a number next to each representing how many of the top 2 scores were marked IsDouble (would be 0, 1 or 2).
Here's the SQL, I've tried lots of combinations of adding aliases to the column and the tables, but I've taken them out for simplicity below:
select Night.*
,
( select sum(IIF(IsDouble,1,0)) from
(SELECT top 2 * from Score where NightId=Night.NightId order by Score desc, IsDouble asc, ID)
) as TopTwoMarkedAsDoubles
from Night
This is a bit of speculation. However, some databases have issues with correlation conditions in multiply nested subqueries. MS Access might have this problem.
If so, you can solve this by using aggregation with a where clause that chooses the top two values:
select s.nightid,
sum(IIF(IsDouble, 1, 0)) as TopTwoMarkedAsDoubles
from Score as s
where s.id in (select top 2 s2.id
from score as s2
where s2.nightid = s.nightid
order by s2.score desc, s2.IsDouble asc, s2.id
)
group by s.nightid;
If this works, it is a simply matter to join Night back in to get the additional columns.
Your subquery can only see one level above it. so Night.NightId is totally unknown to it hence why you are being prompted to enter a value. You can use a Group By to get the value you want for each NightId then correlate that back to the original Night table.
Select *
From Night
left join (
Select N.NightId
, sum(IIF(S.IsDouble,1,0)) as [Number of Doubles]
from Night N
inner join Score S
on S.NightId = S.NightId
group by N.NightId) NightsWithScores
on Night.NightId = NightsWithScores.NightId
Because of the IIF(S.IsDouble,1,0) I don't see the point is using top.
Suppose I have a database of athletic meeting results with a schema as follows
DATE,NAME,FINISH_POS
I wish to do a query to select all rows where an athlete has competed in at least three events without winning. For example with the following sample data
2013-06-22,Johnson,2
2013-06-21,Johnson,1
2013-06-20,Johnson,4
2013-06-19,Johnson,2
2013-06-18,Johnson,3
2013-06-17,Johnson,4
2013-06-16,Johnson,3
2013-06-15,Johnson,1
The following rows:
2013-06-20,Johnson,4
2013-06-19,Johnson,2
Would be matched. I have only managed to get started at the following stub:
select date,name FROM table WHERE ...;
I've been trying to wrap my head around the where clause but I can't even get a start
I think this can be even simpler / faster:
SELECT day, place, athlete
FROM (
SELECT *, min(place) OVER (PARTITION BY athlete
ORDER BY day
ROWS 3 PRECEDING) AS best
FROM t
) sub
WHERE best > 1
->SQLfiddle
Uses the aggregate function min() as window function to get the minimum place of the last three rows plus the current one.
The then trivial check for "no win" (best > 1) has to be done on the next query level since window functions are applied after the WHERE clause. So you need at least one CTE of sub-select for a condition on the result of a window function.
Details about window function calls in the manual here. In particular:
If frame_end is omitted it defaults to CURRENT ROW.
If place (finishing_pos) can be NULL, use this instead:
WHERE best IS DISTINCT FROM 1
min() ignores NULL values, but if all rows in the frame are NULL, the result is NULL.
Don't use type names and reserved words as identifiers, I substituted day for your date.
This assumes at most 1 competition per day, else you have to define how to deal with peers in the time line or use timestamp instead of date.
#Craig already mentioned the index to make this fast.
Here's an alternative formulation that does the work in two scans without subqueries:
SELECT
"date", athlete, place
FROM (
SELECT
"date",
place,
athlete,
1 <> ALL (array_agg(place) OVER w) AS include_row
FROM Table1
WINDOW w AS (PARTITION BY athlete ORDER BY "date" ASC ROWS BETWEEN 3 PRECEDING AND CURRENT ROW)
) AS history
WHERE include_row;
See: http://sqlfiddle.com/#!1/fa3a4/34
The logic here is pretty much a literal translation of the question. Get the last four placements - current and the previous 3 - and return any rows in which the athlete didn't finish first in any of them.
Because the window frame is the only place where the number of rows of history to consider is defined, you can parameterise this variant unlike my previous effort (obsolete, http://sqlfiddle.com/#!1/fa3a4/31), so it works for the last n for any n. It's also a lot more efficient than the last try.
I'd be really interested in the relative efficiency of this vs #Andomar's query when executed on a dataset of non-trivial size. They're pretty much exactly the same on this tiny dataset. An index on Table1(athlete, "date") would be required for this to perform optimally on a large data set.
; with CTE as
(
select row_number() over (partition by athlete order by date) rn
, *
from Table1
)
select *
from CTE cur
where not exists
(
select *
from CTE prev
where prev.place = 1
and prev.athlete = cur.athlete
and prev.rn between cur.rn - 3 and cur.rn
)
Live example at SQL Fiddle.
I have the below query. The problem is the last column productdesc is returning two records and the query fails because of distinct. Now i need to add one more column in where clause of the select query so that it returns one record. The issue is that the column i need
to add should not be a part of group by clause.
SELECT product_billing_id,
billing_ele,
SUM(round(summary_net_amt_excl_gst/100)) gross,
(SELECT DISTINCT description
FROM RES.tariff_nt
WHERE product_billing_id = aa.product_billing_id
AND billing_ele = aa.billing_ele) productdescr
FROM bil.bill_sum aa
WHERE file_id = 38613 --1=1
AND line_type = 'D'
AND (product_billing_id, billing_ele) IN (SELECT DISTINCT
product_billing_id,
billing_ele
FROM bil.bill_l2 )
AND trans_type_desc <> 'Change'
GROUP BY product_billing_id, billing_ele
I want to modify the select statement to the below way by adding a new filter to the where clause so that it returns one record .
(SELECT DISTINCT description
FROM RRES.tariff_nt
WHERE product_billing_id = aa.product_billing_id
AND billing_ele = aa.billing_ele
AND (rate_structure_start_date <= TO_DATE(aa.p_effective_date,'yyyymmdd')
AND rate_structure_end_date > TO_DATE(aa.p_effective_date,'yyyymmdd'))
) productdescr
The aa.p_effective_date should not be a part of GROUP BY clause. How can I do it? Oracle is the Database.
So there are multiple RES.tariff records for a given product_billing_id/billing_ele, differentiated by the start/end dates
You want the description for the record that encompasses the 'p_effective_date' from bil.bill_sum. The kicker is that you can't (or don't want to) include that in the group by. That suggests you've got multiple rows in bil.bill_sum with different effective dates.
The issue is what do you want to happen if you are summarising up those multiple rows with different dates. Which of those dates do you want to use as the one to get the description.
If it doesn't matter, simply use MIN(aa.p_effective_date), or MAX.
Have you looked into the Oracle analytical functions. This is good link Analytical Functions by Example