The result of my SQL Server query returns 3 columns.
Select Id, InItemId, Qty
from Mytable
order by InItemId
I need to add a column, call it row, that starts from 1 and will increase by 1, based on the initemid column with same value.
So the result should be:
Thank you !
Use row_number():
select row_number() over (partition by initemid order by initemid) as row,
t.*
from t;
Note: There is no ordering within a given value of initemid. SQL tables represent unordered sets and there is no obvious column to use for ordering.
Related
A question on using Top. For example, we have this SQL statement:
SELECT TOP (5) WITH TIES orderid, orderdate, custid, empid
FROM Sales.Orders
ORDER BY orderdate DESC;
It orders return rows by orderdate first then select the top most five rows.
But isn't that ORDER clause happens after SELECT clause, which means that the first five order in random will be returned first then those five rows are ordered by orderdate?
The order of commands in the statement doesn't reflect the actual order of operations that SQL follows. See this article which shows the order to be:
from
where
group by
having
select
order by
limit
As you can see, the TOP operation (limit) is the last to be executed.
Question has already an accepted answer. But I would like to quote content from Microsoft Documentation.
Logical Processing Order of the SELECT statement
FROM
ON
JOIN
WHERE
GROUP BY
WITH CUBE or WITH ROLLUP
HAVING
SELECT
DISTINCT
ORDER BY
TOP
But isn't that ORDER clause happens after SELECT clause, which means
that the first five order in random will be returned first then those
five rows are ordered by orderdate ?
No. ORDER BY is processed after the SELECT, but limiting the result set to 5 rows happens even later.
The physical details of actual query processing may vary, but the end result would be as if the server sorted the whole table by orderdate, then picked the top 5 (or more if needed due to ties) rows, return those rows and discard the rest.
I am trying to calculate the Nth percentile of all of the values in a single column in a table. All I want is a scalar, aggregate value for which N percent of the values are below. For instance, If the table has 100 rows where the value is the same as the row index plus one (1 to 100 consecutively), then I'd want this value to tell me that 95% of the values are below 95.
The PERCENTILE_CONT analytic function looks closest to what I want. But if I try to use it like this:
SELECT PERCENTILE_CONT(0.95) WITHIN GROUP (ORDER BY ValueColumn) OVER () AS P95
I get one row per row in the table, all with the same value. I could use TOP 1 to just give me one of those rows, but now I've done an additional table scan.
I am not trying to create a wizbang table of results partitioned by some other column in the original table. I just want an aggregate, scalar value.
Edit: I have been able to use PERCENTILE_CONT in a query with a WHERE clause. For example:
DECLARE #P95 INT
SELECT TOP 1 #P95 = (PERCENTILE_CONT(0.95) WITHIN GROUP (ORDER BY ValueColumn) OVER ())
FROM ExampleTable
WHERE LOWER(Color) = 'blue'
SELECT #P95
Including the WHERE clause gives a different result than I got without it.
From what I can tell, you will need to do a subquery here. For example, to find the number of records strictly below the 95 percentile we can try:
WITH cte AS (
SELECT ValueColumn,
PERCENTILE_CONT(0.95) WITHIN GROUP (ORDER BY ValueColumn) OVER () AS P95
FROM yourTable
)
SELECT COUNT(*)
FROM cte
WHERE ValueColumn < P95;
I'm fairly new to Microsoft SQL Server, so maybe this is very simple yet I just don't have the experience to pull from.
The data I have is similar to the first three columns shown (A, B, C). I want to use those columns to return the data in the yellow highlighted column (D). Basically, I'm trying to show all values of a variable from the current week onward, including when there are change points of the variable. The value of the variable should continue forward in time until the value of the variable changes (column C).
Thanks in advance.
SELECT T1.*, COALESCE(SQ.NewValue, T1.StartingValue) FROM YourTable T1
OUTER APPLY (SELECT TOP 1 T2.NewValue FROM YourTable T2
WHERE T1.Week <= T2.week AND
T2.NewValue IS NOT NULL
ORDER BY T2.Week DESC) SQ
One way is to make Column D a correlated sub-query that gets the most recent previous value of C that is not NULL.
One method, which doesn't need 2 table scans is to use a CTE to create a "group number" and then the OVER clause with a MAX:
WITH VTE AS (
SELECT *
FROM (VALUES(1,0.5,NULL),
(2,0.5,1),
(3,0.5,NULL),
(4,0.5,NULL),
(5,0.5,0.8),
(6,0.5,NULL)) V(WeekNo, Starting, New)),
CTE AS(
SELECT *,
COUNT(New) OVER (ORDER BY WeekNo ASC ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS Grp
FROM VTE)
SELECT WeekNo, Starting, New,
ISNULL(MAX(New) OVER (PARTITION BY CTE.Grp),Starting) AS Result
FROM CTE
ORDER BY WeekNo;
I've been using the following inherited query where I'm trying to delete duplicate rows and I'm getting some unexpected results when first running it as a SELECT - I believe it has something to do with my lack of understanding of the Partition part of the statement:
WITH CTE AS(
SELECT [Id],
[Url],
[Identifier],
[Name],
[Entity],
[DOB],
RN = ROW_NUMBER()OVER(PARTITION BY Name ORDER BY Name)
FROM Data.Statistics
where Id = 2170
)
DELETE FROM CTE WHERE RN > 1
Can someone help me understand exactly what I'm doing with the Partition BY Name part of this? This doesn't limit the query in any way to only looking for duplicates in the Name field, correct? I need to ensure that it's looking for records where all 5 of the fields inside the CTE definition are the same for a record to be considered a duplicate.
ROW_NUMBER() OVER (PARTITION BY Name ORDER BY Name) doesn't make a lot of sense. You wouldn't ORDER BY the same thing you used in PARTITION BY since it will be the same value for everything in the partition, making the ORDER BY part useless.
Basically the CTE part of this query is saying to split the matching rows (those with [Id] = 2170) temporarily into groups for each distinct name, and within each group of rows with the same name, order those by name (which are obviously all the same value) and then return the row number within that sequence group as RN. Unique names will all have a row number of 1, because there is only one row with that name. Duplicate names will have row numbers 1, 2, 3, and so on. The order of those rows is undefined in this case because of the silly ORDER BY clause, but if you changed the ORDER BY to something meaningful, the row numbers would follow that sequence.
I've multipe uniond statements in MSSQL Server that is very hard to find a unique column among the result.
I need to have a unique value per each row, so I've used ROW_NUMBER() function.
This result set is being copied to other place (actually a SOLR index).
In the next time I will run the same query, I need to pick only the newly added rows.
So, I need to confirm that, the newly added rows will be numbered afterward the last row_number value of the last time.
In other words, Is the ROW_NUMBER functions orders the results with the insertion order - suppose I don't adding any ORDER BY clause?
If no, (as I think), Is there any alternatives?
Thanks.
Without seeing the sql I can only give the general answer that MS Sql does not guarantee the order of select statements without an order clause so that would mean that the row_number may not be the insertion order.
I guess you can do something like this..
;WITH
cte
AS
(
SELECT * , rn = ROW_NUMBER() OVER (ORDER BY SomeColumn)
FROM
(
/* Your Union Queries here*/
)q
)
INSERT INTO Destination_Table
SELECT * FROM
CTE LEFT JOIN Destination_Table
ON CTE.Refrencing_Column = Destination_Table.Refrencing_Column
WHERE Destination_Table.Refrencing_Column IS NULL
I would suggest you consider 'timestamping' the row with the time it was inserted. Or adding an identity column to the table.
But what it sounds like you want to do is get current max id and then add the row_number to it.
Select col1, col2, mid + row_number() over(order by smt) id
From (
Select col1, col2, (select max(id) from tbl) mid
From query
) t