query for a range of records in result - tsql

I am wondering if there is some easy way, a function, or other method to return data from a query with the following results.
I have a SQL Express DB 2008 R2, a table that contains numerical data in a given column, say col T.
I am given a value X in code and would like to return up to three records. The record where col T equals my value X, and the record before and after, and nothing else. The sort is done on col T. The record before may be beginning of file and therefore not exist, likewise, if X equals the last record then the record after would be non existent, end of file/table.
The value of X may not exist in the table.
This I think is similar to get a range of results in numerical order.
Any help or direction in solving this would be greatly appreciated.
Thanks again,


It might not be the most optimal solution, but:
SELECT T
FROM theTable
WHERE T = X
UNION ALL
SELECT *
FROM
(
SELECT TOP 1 T
FROM theTable
WHERE T > X
ORDER BY T
) blah
UNION ALL
SELECT *
FROM
(
SELECT TOP 1 T
FROM theTable
WHERE T < X
ORDER BY T DESC
) blah2


DECLARE #x int = 100
;WITH t as
(
select ROW_NUMBER() OVER (ORDER BY T ASC) AS row_nm,*
from YourTable
)
, t1 as
(
select *
from t
WHERE T = #x
)
select *
from t
CROSS APPLY t1
WHERE t.row_nm BETWEEN t1.row_nm -1 and t1.row_nm + 1

Related

Express Nearest Neighbor Join in Postgresql?

I have two tables Q and T, both containing a column of float numbers.
What I want to do is, for each number in Q, I want to find a number in T that has the smallest distance to it.
For example, for T={1,7,9} and Q={2,6,10}, I want to return Q,T pairs as {(2,1),(6,7),(10,9)}.
How should I express this query with SQL?
In addition, is that possible to accelerate this join by index, e.g. add an operator class which bind "FOR ORDER BY <->" with fabs calculation?

create table t (val_t integer);
create table q (val_q integer);
insert into t values (1),(7),(9);
insert into q values (2),(6),(10);
Start with a query that cross joins the two tables and adds a rank based on the difference:
SELECT val_q, val_t, rank() OVER (PARTITION BY val_q ORDER BY abs(val_t - val_q))
FROM t
JOIN q ON true ;
Use this query in a cte or subquery and filter by rank:
WITH src AS(
SELECT val_q, val_t, rank() OVER (PARTITION BY val_q ORDER BY abs(val_t - val_q))
FROM t
JOIN q ON true )
SELECT val_q, val_t FROM src
WHERE rank = 1;
val_q | val_t
-------+-------
2 | 1
6 | 7
10 | 9
See https://www.postgresql.org/docs/12/tutorial-window.html

Given this schema:
create table t (tn float);
insert into t values (1), (7), (9);
create table q (qn float);
insert into q values (2), (6), (10);
DISTINCT ON is the most straightforward way:
select distinct on (qn) qn, tn
from q
cross join t
order by qn, abs(qn - tn);
Exploiting a numeric range may perform better depending on your data sizes. If performance is an issue, then you can create an actual temp table for the range_tn CTE and put a gist index on it:
with all_tn as (
select tn
from t
union select null
), range_tn as (
select numrange(tn::numeric, (lead(tn) over w)::numeric, '[]') as tr
from all_tn
window w as (order by tn nulls first)
)
select qn,
case
when lower_inf(tr) then upper(tr)
when upper_inf(tr) then lower(tr)
when 2 * qn - lower(tr) - upper(tr) > 0 then upper(tr)
else lower(tr)
end as tn
from q
join range_tn
on qn::numeric <# tr;
Fiddle here

find rows not following by the same values in 3 columns

I have a table named raw_data with the following data
as You can see id 1 and 2 share the same values in field desa, kecamatan and kabupaten, also id 3,4,5.
So basically I want to select all rows that is not followed by the same previous values. expected result would be:
I know it's easy to do this in any programming languages such as PHP, but I need this in postgresql. is this doable? Thanks in Advance.

Assuming higher id denotes latest row, if a row with same all three columns is present not together and you don't want to filter it out as it doesn't have same values as previous row (order by id or created_date), then you can make use of analytic lag() function:
select *
from (
select
t.*,
case
when desa = lag(desa) over (order by id)
and kecamatan = lag(kecamatan) over (order by id)
and kabupaten = lag(kabupaten) over (order by id)
then 0 else 1
end flag
from your_table t
) t where flag = 1;

Firebird get the list with all available id

In a table I have records with id's 2,4,5,8. How can I receive a list with values 1,3,6,7. I have tried in this way
SELECT t1.id + 1
FROM table t1
WHERE NOT EXISTS (
SELECT *
FROM table t2
WHERE t2.id = t1.id + 1
)
but it's not working correctly. It doesn't bring all available positions.
Is it possible without another table?

You can get all the missing ID's from a recursive CTE, like this:
with recursive numbers as (
select 1 number
from rdb$database
union all
select number+1
from rdb$database
join numbers on numbers.number < 1024
)
select n.number
from numbers n
where not exists (select 1
from table t
where t.id = n.number)
the number < 1024 condition in my example limit the query to the max 1024 recursion depth. After that, the query will end with an error. If you need more than 1024 consecutive ID's you have either run the query multiple times adjusting the interval of numbers generated or think in a different query that produces consecutive numbers without reaching that level of recursion, which is not too difficult to write.

How do you get the values of rows 10-20 in T-SQL?

Is it possible to get the values of just rows 10 through 20? If so how?

If you're using SQL Server 2005 or greater, check out the ROW_NUMBER function: http://msdn.microsoft.com/en-us/library/ms186734.aspx

One way is to do something like the following...
SELECT * FROM (
SELECT TOP x * FROM (
SELECT TOP y fields
FROM table
WHERE conditions
ORDER BY table.field ASC) as foo
ORDER by field DESC) as bar
ORDER by field ASC
x is the number of rows you want returned and y is x+offset.
http://josephlindsay.com/archives/2005/05/27/paging-results-in-ms-sql-server/

Hey, by the asnwer of joelt about row_number(). I did it.
Its like this:
SELECT allianceId, position, points from (select ROW_NUMBER() over (Order by Points DESC) as position, points, allianceId from Alliance) as somethingx where position >= #alliancePosition - 5 and position <= #alliancePosition + 5;

Getting the minimum of two values in SQL

I have two variables, one is called PaidThisMonth, and the other is called OwedPast. They are both results of some subqueries in SQL. How can I select the smaller of the two and return it as a value titled PaidForPast?
The MIN function works on columns, not variables.

SQL Server 2012 and 2014 supports IIF(cont,true,false) function. Thus for minimal selection you can use it like
SELECT IIF(first>second, second, first) the_minimal FROM table
While IIF is just a shorthand for writing CASE...WHEN...ELSE, it's easier to write.

The solutions using CASE, IIF, and UDF are adequate, but impractical when extending the problem to the general case using more than 2 comparison values. The generalized
solution in SQL Server 2008+ utilizes a strange application of the VALUES clause:
SELECT
PaidForPast=(SELECT MIN(x) FROM (VALUES (PaidThisMonth),(OwedPast)) AS value(x))
Credit due to this website:
http://sqlblog.com/blogs/jamie_thomson/archive/2012/01/20/use-values-clause-to-get-the-maximum-value-from-some-columns-sql-server-t-sql.aspx

Use Case:
Select Case When #PaidThisMonth < #OwedPast
Then #PaidThisMonth Else #OwedPast End PaidForPast
As Inline table valued UDF
CREATE FUNCTION Minimum
(#Param1 Integer, #Param2 Integer)
Returns Table As
Return(Select Case When #Param1 < #Param2
Then #Param1 Else #Param2 End MinValue)
Usage:
Select MinValue as PaidforPast
From dbo.Minimum(#PaidThisMonth, #OwedPast)
ADDENDUM:
This is probably best for when addressing only two possible values, if there are more than two, consider Craig's answer using Values clause.

For SQL Server 2022+ (or MySQL or PostgreSQL 9.3+), a better way is to use the LEAST and GREATEST functions.
SELECT GREATEST(A.date0, B.date0) AS date0,
LEAST(A.date1, B.date1, B.date2) AS date1
FROM A, B
WHERE B.x = A.x
With:
GREATEST(value [, ...]) : Returns the largest (maximum-valued) argument from values provided
LEAST(value [, ...]) Returns the smallest (minimum-valued) argument from values provided
Documentation links :
MySQL http://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html
Postgres https://www.postgresql.org/docs/current/functions-conditional.html
SQL Server https://learn.microsoft.com/en-us/sql/t-sql/functions/logical-functions-least-transact-sql

I just had a situation where I had to find the max of 4 complex selects within an update.
With this approach you can have as many as you like!
You can also replace the numbers with aditional selects
select max(x)
from (
select 1 as 'x' union
select 4 as 'x' union
select 3 as 'x' union
select 2 as 'x'
) a
More complex usage
#answer = select Max(x)
from (
select #NumberA as 'x' union
select #NumberB as 'x' union
select #NumberC as 'x' union
select (
Select Max(score) from TopScores
) as 'x'
) a
I'm sure a UDF has better performance.

Here is a trick if you want to calculate maximum(field, 0):
SELECT (ABS(field) + field)/2 FROM Table
returns 0 if field is negative, else, return field.

Use a CASE statement.
Example B in this page should be close to what you're trying to do:
http://msdn.microsoft.com/en-us/library/ms181765.aspx
Here's the code from the page:
USE AdventureWorks;
GO
SELECT ProductNumber, Name, 'Price Range' =
CASE
WHEN ListPrice = 0 THEN 'Mfg item - not for resale'
WHEN ListPrice < 50 THEN 'Under $50'
WHEN ListPrice >= 50 and ListPrice < 250 THEN 'Under $250'
WHEN ListPrice >= 250 and ListPrice < 1000 THEN 'Under $1000'
ELSE 'Over $1000'
END
FROM Production.Product
ORDER BY ProductNumber ;
GO

This works for up to 5 dates and handles nulls. Just couldn't get it to work as an Inline function.
CREATE FUNCTION dbo.MinDate(#Date1 datetime = Null,
#Date2 datetime = Null,
#Date3 datetime = Null,
#Date4 datetime = Null,
#Date5 datetime = Null)
RETURNS Datetime AS
BEGIN
--USAGE select dbo.MinDate('20120405',null,null,'20110305',null)
DECLARE #Output datetime;
WITH Datelist_CTE(DT)
AS (
SELECT #Date1 AS DT WHERE #Date1 is not NULL UNION
SELECT #Date2 AS DT WHERE #Date2 is not NULL UNION
SELECT #Date3 AS DT WHERE #Date3 is not NULL UNION
SELECT #Date4 AS DT WHERE #Date4 is not NULL UNION
SELECT #Date5 AS DT WHERE #Date5 is not NULL
)
Select #Output=Min(DT) FROM Datelist_CTE;
RETURN #Output;
END;

Building on the brilliant logic / code from mathematix and scottyc, I submit:
DECLARE #a INT, #b INT, #c INT = 0;
WHILE #c < 100
BEGIN
SET #c += 1;
SET #a = ROUND(RAND()*100,0)-50;
SET #b = ROUND(RAND()*100,0)-50;
SELECT #a AS a, #b AS b,
#a - ( ABS(#a-#b) + (#a-#b) ) / 2 AS MINab,
#a + ( ABS(#b-#a) + (#b-#a) ) / 2 AS MAXab,
CASE WHEN (#a <= #b AND #a = #a - ( ABS(#a-#b) + (#a-#b) ) / 2)
OR (#a >= #b AND #a = #a + ( ABS(#b-#a) + (#b-#a) ) / 2)
THEN 'Success' ELSE 'Failure' END AS Status;
END;
Although the jump from scottyc's MIN function to the MAX function should have been obvious to me, it wasn't, so I've solved for it and included it here: SELECT #a + ( ABS(#b-#a) + (#b-#a) ) / 2. The randomly generated numbers, while not proof, should at least convince skeptics that both formulae are correct.

Use a temp table to insert the range of values, then select the min/max of the temp table from within a stored procedure or UDF. This is a basic construct, so feel free to revise as needed.
For example:
CREATE PROCEDURE GetMinSpeed() AS
BEGIN
CREATE TABLE #speed (Driver NVARCHAR(10), SPEED INT);
'
' Insert any number of data you need to sort and pull from
'
INSERT INTO #speed (N'Petty', 165)
INSERT INTO #speed (N'Earnhardt', 172)
INSERT INTO #speed (N'Patrick', 174)
SELECT MIN(SPEED) FROM #speed
DROP TABLE #speed
END

Select MIN(T.V) FROM (Select 1 as V UNION Select 2 as V) T

SELECT (WHEN first > second THEN second ELSE first END) the_minimal FROM table