There is a PostgreSQL SQL SELECT results. I need to divide rows into quintiles and update quintil value to the specific row.
Is there some possibility to do this requirement in SELECT without need to do it in application? I would like to avoid situation when I need to select data to application and do the ranking out of PostgreSQL server.
Data example - first column is value, second column is quintil
4859 - 5
4569 - 5
4125 - 4
3986 - 4
3852 - 3
3562 - 3
3452 - 2
3269 - 2
3168 - 1
3058 - 1
Thank you.
There is a window function called "ntile" to produce this: you give it a parameter specifying how many "tiles" the output it covers should be divided into (5 in this case).
For example:
select t.id, ntile(5) over (order by t.id)
from t
See window function tutorial for an introduction to window functions, and window functions for a list of the standard ones supplied.
Related
How can we achieve the same functionality as of 'SEQUENCE' in provided in Netezza?
Please find below the link demonstrating the functionality I would like to achieve in Big query :
[https://www.ibm.com/support/knowledgecenter/en/SSULQD_7.2.1/com.ibm.nz.dbu.doc/r_dbuser_create_sequence.html][1]
I have reviewed RANK() but this is not solving my purpose to the core. Any leads would be appreciated.
in BigQuery Standard SQL you can find two function that can help you here -
GENERATE_ARRAY(start_expression, end_expression\[, step_expression\])
and
GENERATE_DATE_ARRAY(start_date, end_date\[, INTERVAL INT64_expr date_part\])
For example, below code
#standardSQL
SELECT sequence
FROM UNNEST(GENERATE_ARRAY(1, 10, 1)) AS sequence
produces result as
sequence
1
2
3
4
5
6
7
8
9
10
How I can get min difference between two integer fields(value_0 - value)?
value_0 >= value always
value_0 | value
-------------------
15 | 10
12 | 10
15 | 11
11 | 11
Try this:
SELECT MIN(value_0-value) as MinDiff
FROM TableName
WHERE value_0>=value
With the sample data you have given,
Output is 0. (11-11)
See demo in SQL Fiddle.
Read more about MIN() here.
Here is one way:
select min(value_0 - value)
from table t;
This is pretty basic SQL. If you want to see other values on the same row as the minimum, use order by and choose one row:
select (value_0 - value)
from table t
order by (value_0 - value)
limit 1;
The limit 1 works in some databases for getting one row. Others use top 1 in the select clause. Or fetch first 1 rows only. Or even something else.
I am using SQL Server 2008 and navicat. I need to filter search results in the next way:
1. Data - Id
2. 24 - 1
3. 24 - 3
4. 50 - 5
5. 50 - 8
I need to leave only one data with MAX id value (DISTINCT inside query doesn't work because the data I'm looking is not unique), so result should be:
1. Data - Id
3. 24 - 3
5. 50 8
All the rest similar data values should be filtered out. Thanks in advance!
Select Data,Max(ID) From tablename group by Data
I want to define the start of ROW_NUMBER() as 3258170 instead of 1.
I am using the following SQL query
SELECT ROW_NUMBER() over(order by (select 3258170)) as 'idd'.
However, the above query is not working. When I say not working I mean its executing but its not starting from 3258170. Can somebody help me?
The reason I want to specify the row number is I am inserting Rows from one table to another. In the first Table the last record's row number is 3258169 and when I insert new records I want them to have the row number from 3258170.
Just add the value to the result of row_number():
select 3258170 - 1 + row_number() over (order by (select NULL)) as idd
The order by clause of row_number() is specifying what column is used for the order by. By specifying a constant there, you are simply saying "everything has the same value for ordering purposes". It has nothing, nothing at all to do with the first value chosen.
To avoid confusion, I replaced the constant value with NULL. In SQL Server, I have observed that this assigns a sequential number without actually sorting the rows -- an observed performance advantage, but not one that I've seen documented, so we can't depend on it.
I feel this is easier
ROW_NUMBER() OVER(ORDER BY Field) - 1 AS FieldAlias (To start from 0)
ROW_NUMBER() OVER(ORDER BY Field) + 3258169 AS FieldAlias (To start from 3258170)
Sometimes....
The ROW_NUMBER() may not be the best solution especially when there could be duplicate records in the underlying data set (for JOIN queries etc.). This may result in more rows returned than expected. You may consider creating a SEQUENCE which can be in some cases considered a cleaner solution.
i.e.:
CREATE SEQUENCE myRowNumberId
START WITH 1
INCREMENT BY 1
GO
SELECT NEXT VALUE FOR myRowNumberId AS 'idd' -- your query
GO
DROP SEQUENCE myRowNumberId; -- just to clean-up after ourselves
GO
The downside is that sequences may be difficult to use in complex queries with DISTINCT, WINDOW functions etc. See the complete sequence documentation here.
I had a situation where I was importing a hierarchical structure into an application where a seq number had to be unique within each hierarchical level and start at 110 (for ease of subsequent manual insertion). The data beforehand looked like this...
Level Prod Type Component Quantity Seq
1 P00210005 R NZ1500 57.90000000 120
1 P00210005 C P00210005M 1.00000000 120
2 P00210005M R M/C Operation 20.00000000 110
2 P00210005M C P00210006 1.00000000 110
2 P00210005M C P00210007 1.00000000 110
I wanted the row_number() function to generate the new sequence numbers but adding 10 and then multiplying by 10 wasn't achievable as expected. To force the sequence of arithmetic functions you have to enclose the entire row_number(), and partition clause in brackets. You can only perform simple addition and substraction on the row_number() as such.
So, my solution for this problem was
,10*(10+row_number() over (partition by Level order by Type desc, [Seq] asc)) [NewSeq]
Note the position of the brackets to allow the multiplication to occur after the addition.
Level Prod Type Component Quantity [Seq] [NewSeq]
1 P00210005 R NZ1500 57.90000000 120 110
1 P00210005 C P00210005M 1.00000000 120 120
2 P00210005M R M/C Operation 20.00000000 110 110
2 P00210005M C P00210006 1.00000000 110 120
2 P00210005M C P00210007 1.00000000 110 130
ROW_NUMBER() OVER(ORDER BY Field) - 1 AS FieldAlias (To start from 0)
ROW_NUMBER() OVER(ORDER BY Field) - 2862718 AS FieldAlias (To start from 2862718)
The order by clause of row_number() is specifying what column is used for the order by. By specifying a constant there, you are simply saying "everything has the same value for ordering purposes". It has nothing, nothing at all to do with the first value chosen.
I've been playing with sets in SQL Server 2000 and have the following table structure for one of my temp tables (#Periods):
RestCTR HoursCTR Duration Rest
----------------------------------------
1 337 2 0
2 337 46 1
3 337 2 0
4 337 46 1
5 338 1 0
6 338 46 1
7 338 2 0
8 338 46 1
9 338 1 0
10 339 46 1
...
What I'd like to do is to calculate the Sum of the 2 longest Rest periods for each HoursCTR, preferably using sets and temp tables (rather than cursors, or nested subqueries).
Here's the dream query that just won't work in SQL (no matter how many times I run it):
Select HoursCTR, SUM ( TOP 2 Duration ) as LongestBreaks
FROM #Periods
WHERE Rest = 1
Group By HoursCTR
The HoursCTR can have any number of Rest periods (including none).
My current solution is not very elegant and basically involves the following steps:
Get the max duration of rest, group by HoursCTR
Select the first (min) RestCTR row that returns this max duration for each HoursCTR
Repeat step 1 (excluding the rows already collected in step 2)
Repeat step 2 (again, excluding rows collected in step 2)
Combine the RestCTR rows (from step 2 and 4) into single table
Get SUM of the Duration pointed to by the rows in step 5, grouped by HoursCTR
If there are any set functions that cut this process down, they would be very welcome.
The best way to do this in SQL Server is with a common table expression, numbering the rows in each group with the windowing function ROW_NUMBER():
WITH NumberedPeriods AS (
SELECT HoursCTR, Duration, ROW_NUMBER()
OVER (PARTITION BY HoursCTR ORDER BY Duration DESC) AS RN
FROM #Periods
WHERE Rest = 1
)
SELECT HoursCTR, SUM(Duration) AS LongestBreaks
FROM NumberedPeriods
WHERE RN <= 2
GROUP BY HoursCTR
edit: I've added an ORDER BY clause in the partitioning, to get the two longest rests.
Mea culpa, I did not notice that you need this to work in Microsoft SQL Server 2000. That version doesn't support CTE's or windowing functions. I'll leave the answer above in case it helps someone else.
In SQL Server 2000, the common advice is to use a correlated subquery:
SELECT p1.HoursCTR, (SELECT SUM(t.Duration) FROM
(SELECT TOP 2 p2.Duration FROM #Periods AS p2
WHERE p2.HoursCTR = p1.HoursCTR
ORDER BY p2.Duration DESC) AS t) AS LongestBreaks
FROM #Periods AS p1
SQL 2000 does not have CTE's, nor ROW_NUMBER().
Correlated subqueries can need an extra step when using group by.
This should work for you:
SELECT
F.HoursCTR,
MAX (F.LongestBreaks) AS LongestBreaks -- Dummy max() so that groupby can be used.
FROM
(
SELECT
Pm.HoursCTR,
(
SELECT
COALESCE (SUM (S.Duration), 0)
FROM
(
SELECT TOP 2 T.Duration
FROM #Periods AS T
WHERE T.HoursCTR = Pm.HoursCTR
AND T.Rest = 1
ORDER BY T.Duration DESC
) AS S
) AS LongestBreaks
FROM
#Periods AS Pm
) AS F
GROUP BY
F.HoursCTR
Unfortunately for you, Alex, you've got the right solution: correlated subqueries, depending upon how they're structured, will end up firing multiple times, potentially giving you hundreds of individual query executions.
Put your current solution into the Query Analyzer, enable "Show Execution Plan" (Ctrl+K), and run it. You'll have an extra tab at the bottom which will show you how the engine went about the process of gathering your results. If you do the same with the correlated subquery, you'll see what that option does.
I believe that it's likely to hammer the #Periods table about as many times as you have individual rows in that table.
Also - something's off about the correlated subquery, seems to me. Since I avoid them like the plague, knowing that they're evil, I'm not sure how to go about fixing it up.