I have a table that, for the most part, is individual users. Occasionally there is a joint user. For a joint user, all the fields in the table will be exactly the same as the primary user except for a b-score field. I want to only display one row of data per account, and use the highest b-score to decide which row to use when it is a joint account (so the highest score is displayed only)
I thought it would be a simple
SELECT DISTINCT accountNo, MAX(bscore) FROM table, GROUP BY accountNo
but I'm still getting multiple rows for joints
You seem to want the ANSI-standard row_number() function:
select t.*
from (select t.*, row_number() over (partition by accountNo order by bscore desc) as seqnum
from t
) t
where seqnum = 1;
This worked for me, maybe not the most efficient. Correlated sub-query. The key part is accountNo = a.accountNo.
SELECT DISTINCT a.accountNo, (SELECT MAX(bscore) FROM table WHERE accountNo =
a.accountNo) bscore
FROM table a
GROUP BY a.accountNo
Related
How would I include the name of any one of the books that belong to that particular type in the below query?
select distinct
(select sum(ob.Balance)),
ob.BookType
from orders.OrderBooks ob
group by ob.BookType
In its current state it does what I need it to and groups books by BookType and sums their balances, as seen below.
However I need the name of any book that belongs to that BookType as part of the result.
If I select the BookName column and then group by it like below, it results in more unique entries and to an extent undoes the original grouping.
select distinct
(select sum(ob.Balance)),
ob.BookType,
ob.BookName
from orders.OrderBooks ob
group by ob.BookType, ob.BookName
;WITH x AS
(
SELECT
Balance = SUM(Balance) OVER (PARTITION BY BookType),
BookType,
BookName,
rn = ROW_NUMBER() OVER (PARTITION BY BookType ORDER BY BookName DESC)
FROM orders.OrderBooks
)
SELECT Balance, BookType, BookName
FROM x
WHERE rn = 1;
db<>fiddle
ORDER BY BookName DESC was dealer's choice. If you truly don't care which title shows up in the result, you can use any ordering you like. If you want the results to be random every time, you can use ORDER BY NEWID().
In general I like this flexibility better than the TOP (1) subquery approach, in addition to a single scan instead of an additional table access per row. But you can also do it a different way; just take min/max of the bookname, too:
SELECT Balance = SUM(Balance),
BookType,
BookName = MIN(BookName) -- or MAX()
FROM dbo.OrderBooks
GROUP BY BookType;
You can see these give similar results in this db<>fiddle. Plan is simpler, too; most notably: no spools. However when you use an aggregate function against that column, it makes it harder to provide arbitrary/random results, and if you intend to add other columns pulled from the right row, you'll need to go back to the row_number solution.
You can use a correlated subquery to get a single book name of that type. This assumes there's an ID field and you want to pull the most recent one:
select
Balance = (select sum(ob.Balance)),
ob.BookType,
BookName = (SELECT TOP(1) ob.BookName FROM orders.OrderBooks ob2 WHERE ob2.BookType = ob.BookType ORDER BY ob2.ID DESC)
from orders.OrderBooks ob
group by ob.BookType, ob.BookName
I'm relatively new to working with SQL and wasn't able to find any past threads to solve my question. I have three columns in a table, columns being name, customer, and location. I'd like to add an additional column determining which location is most frequent, based off name and customer (first two columns).
I have included a photo of an example where name-Jane customer-BEC in my created column would be "Texas" as that has 2 occurrences as opposed to one for California. Would there be anyway to implement this?
If you want 'Texas' on all four rows:
select t.Name, t.Customer, t.Location,
(select t2.location
from table1 t2
where t2.name = t.name
group by name, location
order by count(*) desc
fetch first 1 row only
) as most_frequent_location
from table1 t ;
You can also do this with analytic functions:
select t.Name, t.Customer, t.Location,
max(location) keep (dense_rank first order by location_count desc) over (partition by name) most_frequent_location
from (select t.*,
count(*) over (partition by name, customer, location) as location_count
from table1 t
) t;
Here is a db<>fiddle.
Both of these version put 'Texas' in all four rows. However, each can be tweaks with minimal effort to put 'California' in the row for ARC.
In Oracle, you can use aggregate function stats_mode() to compute the most occuring value in a group.
Unfortunately it is not implemented as a window function. So one option uses an aggregate subquery, and then a join with the original table:
select t.*, s.top_location
from mytable t
inner join (
select name, customer, stats_mode(location) top_location
from mytable
group by name, customer
) s where s.name = t.name and s.customer = t.customer
You could also use a correlated subquery:
select
t.*,
(
select stats_mode(t1.location)
from mytable t1
where t1.name = t.name and t1.customer = t.customer
) top_location
from mytable t
This is more a question about understanding the concepts of a relational database. If you want that information, you would not put that in an additional column. It is calculated data over multiple columns - why would you store that in the table itself ? It is complex to code and it would also be very expensive for the database (imagine all the rows you have to calculate that value for if someone inserted a million rows)
Instead you can do one of the following
Calculate it at runtime, as shown in the other answers
if you want to make it more persisent, you could embed that query above in a view
if you want to physically store the info, you could use a materialized view
Plenty of documentation on those 3 options in the official oracle documentation
Your first step is to construct a query that determines the most frequent location, which is as simple as:
select Name, Customer, Location, count(*)
from table1
group by Name, Customer, Location
This isn't immediately useful, but the logic can be used in row_number(), which gives you a unique id for each row returned. In the query below, I'm ordering by count(*) in descending order so that the most frequent occurrence has the value 1.
Note that row_number() returns '1' to only one row.
So, now we have
select Name, Customer, Location, row_number() over (partition by Name, Customer order by count(*) desc) freq_name_cust
from table1 tb_
group by Name, Customer, Location
The final step puts it all together:
select tab.*, tb_.Location most_freq_location
from table1 tab
inner join
(select Name, Customer, Location, row_number() over (partition by Name, Customer order by count(*) desc) freq_name_cust
from table1
group by Name, Customer, Location) tb_
on tb_.Name = tab.Name
and tb_.Customer = tab.Customer
and freq_name_cust = 1
You can see how it all works in this Fiddle where I deliberately inserted rows with the same frequency for California and Texas for one of the customers for illustration purposes.
I'm trying to gather the entire row information associated with the MAX() of a particular field.
I essentially have several [Flight_Leg] for a unique [Shipment_ID], and each one has unique [Destination_Aiport], [Departure_Time], and [Arrival_Time]. Obviously, each [Shipment_ID] can have multiple [Flight_Leg], and each [Flight_Leg] has a unique row of information.
SELECT
[Shipment_ID],
MAX([Flight_Leg]) AS "Final Leg",
[Arrival_Time],
[Destination_Airport]
FROM
[Flight_Info]
Group By
[Shipment_ID],
[Arrival_Time]
The output is multiple lines, rather than having one unique line for [Shipment_ID]. I'm just trying to isolate the FINAL flight info for a shipment.
Depending on your database, most support window functions. Here's one option using row_number():
select *
from (
select *, row_number() over (partition by shipment_id order by flight_leg desc) rn
from flight_info
) t
where rn = 1
Alternatively here's a more generic approach joining back to itself:
select fi.*
from flight_info fi
join (select shipment_id, max(flight_leg) max_flight_leg
from flight_info
group by shipment_id) t on fi.shipment_id = t.shipment_id
and fi.flight_leg = t.max_flight_leg
I want to write a SQL query to generate ranks of groups and subgroups based on third column (Price in this case). While i know we can use dense_rank() to generate ranks based on one column. I have no idea how to generate the two columns of ranks as shown below in a single query.
Both the rankings are based on price. So J3 comes first because J3 sum(price) is 1600. J1 comes second because J1 sum(price) is 1500 and so on.
Any inputs are appreciated.
I have provided the sample input and output. The name of the input table is "RENTAL"
First roll up jet_type prices to the jet_type level, then create a ranking of all jet_types ordered by rolled up price, and finally use your window function in the outer query partitioned by jet_price and ordered by highest rolled up price to create rank_service_wthin_jet:
select a.jet_type, b.rownum rank_jet, a.service_type, a.price,
row_number() over(partition by a.jet_type order by a.price desc) rank_service_wthin_jet
from yourtable a join (
select jet_type, row_number() over(order by price desc) rownum from (
select jet_type, sum(price) price from yourtable
group by jet_type)a)b on a.jet_type=b.jet_type
You can generate two columns as:
select t.*,
dense_rank() over (order by jet_type) as rank_jet,
row_number() over (partition by jet_type order by price desc) as rank_service_within_jet
. . .
This does not exactly return what is in your table. But the results are quite similar and -- even more important -- make sense.
I want to use the ROW_NUMBER() to get...
To get the max(ROW_NUMBER()) --> Or i guess this would also be the count of all rows
I tried doing:
SELECT max(ROW_NUMBER() OVER(ORDER BY UserId)) FROM Users
but it didn't seem to work...
To get ROW_NUMBER() using a given piece of information, ie. if I have a name and I want to know what row the name came from.
I assume it would be something similar to what I tried for #1
SELECT ROW_NUMBER() OVER(ORDER BY UserId) From Users WHERE UserName='Joe'
but this didn't work either...
Any Ideas?
For the first question, why not just use?
SELECT COUNT(*) FROM myTable
to get the count.
And for the second question, the primary key of the row is what should be used to identify a particular row. Don't try and use the row number for that.
If you returned Row_Number() in your main query,
SELECT ROW_NUMBER() OVER (Order by Id) AS RowNumber, Field1, Field2, Field3
FROM User
Then when you want to go 5 rows back then you can take the current row number and use the following query to determine the row with currentrow -5
SELECT us.Id
FROM (SELECT ROW_NUMBER() OVER (ORDER BY id) AS Row, Id
FROM User ) us
WHERE Row = CurrentRow - 5
Though I agree with others that you could use count() to get the total number of rows, here is how you can use the row_count():
To get the total no of rows:
with temp as (
select row_number() over (order by id) as rownum
from table_name
)
select max(rownum) from temp
To get the row numbers where name is Matt:
with temp as (
select name, row_number() over (order by id) as rownum
from table_name
)
select rownum from temp where name like 'Matt'
You can further use min(rownum) or max(rownum) to get the first or last row for Matt respectively.
These were very simple implementations of row_number(). You can use it for more complex grouping. Check out my response on Advanced grouping without using a sub query
If you need to return the table's total row count, you can use an alternative way to the SELECT COUNT(*) statement.
Because SELECT COUNT(*) makes a full table scan to return the row count, it can take very long time for a large table. You can use the sysindexes system table instead in this case. There is a ROWS column that contains the total row count for each table in your database. You can use the following select statement:
SELECT rows FROM sysindexes WHERE id = OBJECT_ID('table_name') AND indid < 2
This will drastically reduce the time your query takes.
You can use this for get first record where has clause
SELECT TOP(1) * , ROW_NUMBER() OVER(ORDER BY UserId) AS rownum
FROM Users
WHERE UserName = 'Joe'
ORDER BY rownum ASC
ROW_NUMBER() returns a unique number for each row starting with 1. You can easily use this by simply writing:
ROW_NUMBER() OVER (ORDER BY 'Column_Name' DESC) as ROW_NUMBER
May not be related to the question here. But I found it could be useful when using ROW_NUMBER -
SELECT *,
ROW_NUMBER() OVER (ORDER BY (SELECT 100)) AS Any_ID
FROM #Any_Table
select
Ml.Hid,
ml.blockid,
row_number() over (partition by ml.blockid order by Ml.Hid desc) as rownumber,
H.HNAME
from MIT_LeadBechmarkHamletwise ML
join [MT.HAMLE] h on ML.Hid=h.HID
SELECT num, UserName FROM
(SELECT UserName, ROW_NUMBER() OVER(ORDER BY UserId) AS num
From Users) AS numbered
WHERE UserName='Joe'
You can use Row_Number for limit query result.
Example:
SELECT * FROM (
select row_number() OVER (order by createtime desc) AS ROWINDEX,*
from TABLENAME ) TB
WHERE TB.ROWINDEX between 0 and 10
--
With above query, I will get PAGE 1 of results from TABLENAME.
If you absolutely want to use ROW_NUMBER for this (instead of count(*)) you can always use:
SELECT TOP 1 ROW_NUMBER() OVER (ORDER BY Id)
FROM USERS
ORDER BY ROW_NUMBER() OVER (ORDER BY Id) DESC
Need to create virtual table by using WITH table AS, which is mention in given Query.
By using this virtual table, you can perform CRUD operation w.r.t row_number.
QUERY:
WITH table AS
-
(SELECT row_number() OVER(ORDER BY UserId) rn, * FROM Users)
-
SELECT * FROM table WHERE UserName='Joe'
-
You can use INSERT, UPDATE or DELETE in last sentence by in spite of SELECT.
SQL Row_Number() function is to sort and assign an order number to data rows in related record set. So it is used to number rows, for example to identify the top 10 rows which have the highest order amount or identify the order of each customer which is the highest amount, etc.
If you want to sort the dataset and number each row by seperating them into categories we use Row_Number() with Partition By clause. For example, sorting orders of each customer within itself where the dataset contains all orders, etc.
SELECT
SalesOrderNumber,
CustomerId,
SubTotal,
ROW_NUMBER() OVER (PARTITION BY CustomerId ORDER BY SubTotal DESC) rn
FROM Sales.SalesOrderHeader
But as I understand you want to calculate the number of rows of grouped by a column. To visualize the requirement, if you want to see the count of all orders of the related customer as a seperate column besides order info, you can use COUNT() aggregation function with Partition By clause
For example,
SELECT
SalesOrderNumber,
CustomerId,
COUNT(*) OVER (PARTITION BY CustomerId) CustomerOrderCount
FROM Sales.SalesOrderHeader
This query:
SELECT ROW_NUMBER() OVER(ORDER BY UserId) From Users WHERE UserName='Joe'
will return all rows where the UserName is 'Joe' UNLESS you have no UserName='Joe'
They will be listed in order of UserID and the row_number field will start with 1 and increment however many rows contain UserName='Joe'
If it does not work for you then your WHERE command has an issue OR there is no UserID in the table. Check spelling for both fields UserID and UserName.