set search_path='tmp';
DROP TABLE lutser;
CREATE TABLE lutser
( val float
, num bigint
);
INSERT INTO lutser(val, num)
VALUES ( 0.1133 , 2312882332 )
,( 4.3293 , 7876123213 )
,( 3.1133 , 2312332332 )
,( 1.3293 , 7876543213 )
,( 0.0033 , 2312222332 )
,( 5.3293 , 5344343213 )
,( 3.2133 , 4122331112 )
,( 2.3293 , 9999942333 )
;
WITH ranked_lutsers AS (
SELECT val, num
,rank() OVER (ORDER BY val) AS rnk
FROM lutser
)
SELECT that.val, that.num
, (that.rnk-this.rnk) AS relrnk
FROM ranked_lutsers that
JOIN ranked_lutsers this ON (that.rnk BETWEEN this.rnk-2 AND this.rnk+2)
WHERE this.val = 1.3293
;
结果:
DROP TABLE
CREATE TABLE
INSERT 0 8
val | num | relrnk
--------+------------+--------
0.0033 | 2312222332 | -2
0.1133 | 2312882332 | -1
1.3293 | 7876543213 | 0
2.3293 | 9999942333 | 1
3.1133 | 2312332332 | 2
(5 rows)
正如 Erwin 指出的那样,输出中不需要中间行。此外,应该使用 row_number() 而不是 rank()。
WITH ranked_lutsers AS (
SELECT val, num
-- ,rank() OVER (ORDER BY val) AS rnk
, row_number() OVER (ORDER BY val, num) AS rnk
FROM lutser
) SELECT that.val, that.num
, (that.rnk-this.rnk) AS relrnk
FROM ranked_lutsers that
JOIN ranked_lutsers this ON (that.rnk BETWEEN this.rnk-2 AND this.rnk+2 )
WHERE this.val = 1.3293
AND that.rnk <> this.rnk
;
结果2:
val | num | relrnk
--------+------------+--------
0.0033 | 2312222332 | -2
0.1133 | 2312882332 | -1
2.3293 | 9999942333 | 1
3.1133 | 2312332332 | 2
(4 rows)
UPDATE2:总是选择四个,即使我们在列表的顶部或底部。这使得查询有点难看。(但不像欧文那样丑;-)
WITH ranked_lutsers AS (
SELECT val, num
-- ,rank() OVER (ORDER BY val) AS rnk
, row_number() OVER (ORDER BY val, num) AS rnk
FROM lutser
) SELECT that.val, that.num
, ABS(that.rnk-this.rnk) AS srtrnk
, (that.rnk-this.rnk) AS relrnk
FROM ranked_lutsers that
JOIN ranked_lutsers this ON (that.rnk BETWEEN this.rnk-4 AND this.rnk+4 )
-- WHERE this.val = 1.3293
WHERE this.val = 0.1133
AND that.rnk <> this.rnk
ORDER BY srtrnk ASC
LIMIT 4
;
输出:
val | num | srtrnk | relrnk
--------+------------+--------+--------
0.0033 | 2312222332 | 1 | -1
1.3293 | 7876543213 | 1 | 1
2.3293 | 9999942333 | 2 | 2
3.1133 | 2312332332 | 3 | 3
(4 rows)
更新:具有嵌套 CTE 的版本(具有外连接!!!)。为了方便起见,我在表中添加了一个主键,无论如何,恕我直言,这听起来是个好主意。
WITH distance AS (
WITH ranked_lutsers AS (
SELECT id
, row_number() OVER (ORDER BY val, num) AS rnk
FROM lutser
) SELECT l0.id AS one
,l1.id AS two
, ABS(l1.rnk-l0.rnk) AS dist
-- Warning: Cartesian product below
FROM ranked_lutsers l0
, ranked_lutsers l1 WHERE l0.id <> l1.id
)
SELECT lu.*
FROM lutser lu
JOIN distance di
ON lu.id = di.two
WHERE di.one= 1
ORDER by di.dist
LIMIT 4
;