CODEWITHSUNDEEP
sqlmysql
azera
azera

Reputation: 231

Select the X "closest" ids?

Let's say you have a table with a integer primary key named 'table_id'

Is it possible in a single query to extract the row with a specific id AND the X row before it AND the X row after it ?

For exemple, if your ids are (1,2,8,12,16,120,250,354), X is 2 and the id you have is 16, the select should return rows with ids 8,12,16,120,250

i know how to do it with several queries, I'm wondering about doing that in a single pass (sub queries, union and all are fine).

Thanks for any help

Upvotes: 5

Views: 1067

Answers (6)

Disillusioned
Disillusioned

Reputation: 14832

Try the following: Unfortunately, I don't have MySQL, but the MS SQL Server version works.

SELECT  /*TOP (2*2 +1)    --MS SQL Server syntax */
        *
FROM    IDTable
WHERE   IDCol >= (
        SELECT  MIN(IDCol)
        FROM    (
                SELECT  /*TOP 2   --MS SQL Server syntax */
                        IDCol
                FROM    IDTable
                WHERE   IDCol < 16
                ORDER BY IDCol DESC limit 2
                ) t
        )
ORDER BY IDCol limit (2*2 +1)

Upvotes: 0

Joe Zack
Joe Zack

Reputation: 3308

Here's how I would do it, it's simple and it works for signed/unsigned numbers:

-- Finds the closest 5 productID's to 200
SELECT     productID, abs(productID - 200) as diff
FROM       products
WHERE      productID != 200
ORDER BY   diff, productID
LIMIT      5

If you're using unsigned numbers, then you'll need to cast the column first:

-- Finds the closest 5 productID's to 200 (unsigned)
SELECT     productID, abs(CAST(productID as SIGNED) - 200) as diff
FROM       products
WHERE      productID != 200
ORDER BY   diff, productID
LIMIT      5

Upvotes: 0

Ben Collins
Ben Collins

Reputation: 484

This works in SQL Server using a derived query:

DECLARE @X int, @target_id int

SET @X = 2
SET @target_id = 8

SELECT [table_id]
FROM
(SELECT TOP ((@X * 2) + 1) [table_id]
      ,ABS(@target_id - [table_id]) AS [Diff]
  FROM [tblItems]
  ORDER BY [Diff] ASC) T
ORDER BY table_id ASC
GO

Upvotes: 0

pstanton
pstanton

Reputation: 36640

try this:

select table_id from table where id > 16 order by table_id desc limit 2
union all
select table_id from table where id <= 16 order by table_id asc limit 3;

Upvotes: 4

Guffa
Guffa

Reputation: 700352

You can make a union between the items before and the item and the items after, but you have to make them subqueries to order them:

select * from (
  select * from thetable where table_id >= 16 order by table_id limit 3
) x
union all
select * from (
  select * from thetable where table_id < 16 order by table_id desc limit 2
) y
order by table_id

Upvotes: 5

Tatu Ulmanen
Tatu Ulmanen

Reputation: 124778

Using MySQL's LIMIT syntax and UNION:

SELECT table_id FROM table WHERE id > 16 ORDER BY table_id ASC LIMIT 2
UNION
SELECT table_id FROM table WHERE id <= 16 ORDER BY table_id DESC LIMIT 3

Upvotes: 0

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