I'm a new SQL user and need help.
Let's say I have a vehicle number 123 and I've traveled from Region 3 to final destination Region 4. In between, I've visited Region 1 and 5 as well but that's not my concern.
Simple example would be as follow.
Original Table
Desired Output
How can this be done in SQL query?
You have a sequence number so you can use some form of aggregation. One method is:
select records,
max(case when sequence = 1 then fromregion end) as fromregion,
max(case when sequence = maxsequence then toregion) as toregion
from (select t.*, max(sequence) over (partition by records) as max_sequence
from t
) t
group by records;
Unfortunately, SQL Server doesn't offer "first()" or "last()" as aggregation functions. But it does support first_value() as a window function. This allows you to do the logic without a subquery:
select distinct records,
first_value(fromRegion) over (partition by records order by sequence) as fromregion,
first_value(toRegion) over (partition by records order by sequence desc) as toregion
from t;
Related
for example i have data like this(sql server)
id name
4 anu
3 lohi
1 pras
2 chand
i want 2nd record in a table (means 3 lohi)
if i use row_number() function its changes the order and i get (2 chand)
i want 2nd record from table data
can anyonr please give me the query fro above scenario
There is no such thing as the nth row in a table. And for a simple reason: SQL tables represent unordered sets (technically multi-sets because they allow duplicates).
You can do what you want use offset/fetch:
select t.*
from t
order by id desc
offset 1 fetch first 1 row only;
This assumes that the descending ordering on id is what you want, based on your example data.
You can also do this using row_number():
select t.*
from (select t.*,
row_number() over (order by id desc) as seqnum
from t
) t
where seqnum = 2;
I should note that that SQL Server allows you to assign row_number() without having an effective sort using something like this:
select t.*
from (select t.*,
row_number() over (order by (select NULL)) as seqnum
from t
) t
where seqnum = 2;
However, this returns an arbitrary row. There is no guarantee it returns the same row each time it runs, nor that the row is "second" in any meaningful use of the term.
I need to write a stored procedure or SQL statements which needs to be run for around 1M records for an Oracle database. This should fetch the data based on priority as defined.
1 is highest priority and 4 is lowest.
When the records are group by using Cust ID, it should select only that record which is of highest priority as per source name else move to next source for priority within that group.
I am using old school ways by using LISTAGG and then check for value of Source name = A and then fetch all the data.
Is there any better way to extract the information.
The output should only contain records as per priority for each Group BY of Cust ID
You can use the analytical function ROW_NUMBER as follows:
SELECT * FROM
(SELECT T.*, ROW_NUMBER() OVER (PARTITION BY T.CUSTID ORDER BY P.PRIORITY) AS RN
FROM YOUR_TABLE T JOIN PRIORITY_TABLE P
ON T.SOURCE_NAME = P.SOURCE_NAME)
WHERE RN = 1
i have a tbl call it tbl_test in which continously data are inserting and it has approx 10^6 records at a time it has colums
Acquire_Id (Value between 1 to 20 ),
Status_Msg(value between 'A' to 'Z'),
Status_Code(value between 1 to 26)
There is one to one mapping b/w Status_Msg and Status_Code
Now i want to get two most frequent status_msg and Staus_Code Count for each acquirer if they are present in table
Query should be Cost Saving
Most databases support the ANSI standard window functions. You can get what you want using row_number() (or rank() or dense_rank(), depending on how ties are returned) after aggregating the values.
The following returns exactly two rows for each acquirer (even if there are ties).
select t.*
from (select t.acquire_id, t.status_msg, t.status_code, count(*) as cnt,
row_number() over (partition by t.acquire_id order by count(*) desc) as seqnum
from tbl_test t
group by t.acquire_id, t.status_msg, t.status_code
) t
where seqnum <= 2;
I am trying to find whether a person (id = A3) is continuously active in a program at least five months or more in a given year (2013). Any suggestion would be appreciated. My data look like as follows:
You simply use group by and a conditional expression:
select id,
(case when count(ActiveMonthYear) >= 5 then 'YES!' else 'NAW' end)
from table t
where ListOfTheMonths between '201301' and '201312'
group by id;
EDIT:
I suppose "continuously" doesn't just mean any five months. For that, there are various ways. I like the difference of row numbers approach
select distinct id
from (select t.*,
(row_number() over (partition by id order by ListOfTheMonths) -
count(ActiveMonthYear) over (partition by id order by ListOfTheMonths)
) as grp
from table t
where ListOfTheMonths between '201301' and '201312'
) t
where ActiveMonthYear is not null
group by id, grp
having count(*) >= 5;
The difference in the subquery is constant for groups of consecutive active months. This is then used a grouping. The result is a list of all ids that meet this criteria. You can add a where for a particular id (do it in the subquery).
By the way, this is written using select distinct and group by. This is one of the rare cases where these two are appropriately used together. A single id could have two periods of five months in the same year. There is no reason to include that person twice in the result set.
I have a table - Data - of rows, simplified, like so:
Name,Amount,Last,Date
A,16,31,1-Jan-2014
A,27,38,1-Feb-2014
A,12,34,1-Mar-2014
B,8,37,1-Jan-2014
B,3,38,1-Feb-2014
B,17,39,1-Mar-2014
I wish to group them similar to:
select Name,sum(Amount),aggr(Last),max(Date) from Data group by Name
For aggr(Last) I want the value of 'Last' from the row that contains max(Date)
So the result I want would be 2 rows
Name,Amount,Last,Date
A,55,34,1-Mar-2014
B,28,39,1-Mar-2014
i.e. in both cases, the value of Last is the one from the row that contained 1-Mar-2014
The query I'm actually doing is basically the same, but with many more sum() fields and millions of rows, so I'm guessing an aggregate function could avoid multiple extra requests each group of incoming rows.
Instead, use row_number() and conditional aggregation:
select Name, sum(Amount),
max(case when seqnum = 1 then Last end) as Last,
max(date)
from (select d.*, row_number() over (partition by name order by date desc) as seqnum
from data d
) d
group by Name;