Question

有人告诉我要针对一个显然是重复的问题提出一个新问题，如果重复没有给我我想要的正确答案。

因此，我系统的基础是我有一个填充有“房屋”位置/坐标的数据库。我进行了高级查询，选择了某个坐标附近的所有房屋，就像这样；

SELECT id, type, distance FROM (SELECT b.id, b.type, b.x, b.y, b.z, 
    SQRT(POWER(ABS(1654.5413 - b.x), 2) + POWER(ABS(-2293.7571 - b.y), 2) + POWER(ABS(-1.1996 - b.z), 2)) AS "distance" 
        FROM businesses b ORDER BY distance ASC) as T;

这将导致;

+------+------+------------------------+
| id   | type | distance               |
+------+------+------------------------+
| 1953 |    2 | 0.00004489639611771451 |
|    2 |  100 |      8.757256937390904 |
| 1959 |    2 |      8.999959765646956 |
| 1960 |    2 |     10.499959765643807 |
| 1961 |    2 |     11.999959765641446 |
| 1962 |    2 |     13.499959765639607 |
| 1963 |    2 |     14.999959765638138 |
| 1964 |    2 |     16.499959765636934 |
| 2055 |    3 |      17.11486010149676 |
| 2054 |    1 |     17.751048488860313 |
| 1965 |    2 |     17.999959765635932 |
| 1966 |    2 |     19.499959765635083 |
| 1967 |    2 |     20.999959765634358 |
| 2056 |    5 |      22.26658275782834 |
| 1968 |    2 |     22.499959765633726 |
| 1969 |    2 |     23.999959765633175 |
| 2057 |    5 |     24.054132659013334 |
| 1970 |    2 |      25.49995976563269 |
| 2058 |    5 |     26.001138245767084 |
| 2061 |    4 |     26.853239370669378 |
| 1971 |    2 |      26.99995976563226 |
| 1972 |    2 |      28.49995976563187 |
| 2060 |    5 |      28.55999771765475 |
| 1973 |    2 |     29.999959765631523 |
| 2059 |    5 |     31.414688663981224 |
| 1974 |    2 |     31.499959765631207 |
|    1 |  100 |      121468.4587678613 |
+------+------+------------------------+

我基本上想要做的是抓住距离最短的行，但是我不希望基于“类型”列重复行，就像这样；

+------+------+------------------------+
| id   | type | distance               |
+------+------+------------------------+
| 1953 |    2 | 0.00004489639611771451 |
|    2 |  100 |      8.757256937390904 |
| 2055 |    3 |      17.11486010149676 |
| 2054 |    1 |     17.751048488860313 |
| 2056 |    5 |      22.26658275782834 |
| 2061 |    4 |     26.853239370669378 |
+------+------+------------------------+

在上一个问题中我收到了两个答案（都错了），它们都是正确的一半，其中一个答案是;

“使用嵌套查询更简单：

SELECT id,type, MIN(distance) AS 'minDistance'
FROM(
SELECT id, type, distance FROM (SELECT b.id, b.type, b.x, b.y, b.z, 
    SQRT(POWER(ABS(1654.5413 - b.x), 2) + POWER(ABS(-2293.7571 - b.y), 2) + POWER(ABS(-1.1996 - b.z), 2)) AS "distance" 
        FROM businesses b ORDER BY distance ASC) as T) AS TABLE
GROUP BY type 
ORDER BY 'minDistance'

”

^上面的答案确实选择了我期望的正确距离。但是它没有做的是匹配id字段和我要选择的所有其他字段，基本上使具有不同值的行不匹配。不知道我是否正确解释了，但是基本上就是这样。

如果我的表中填充了这些行；

+------+------+------------------------+
| id   | type | distance               |
+------+------+------------------------+
| 1960 |    2 |     65.757256937390904 |
| 1953 |    2 | 0.00004489639611771451 |
| 2055 |    2 |      17.11486010149676 |
+------+------+------------------------+

然后运行从答案中得到的查询，我会得到这个；

+------+------+------------------------+
| id   | type | distance               |
+------+------+------------------------+
| 1960 |    2 | 0.00004489639611771451 |
+------+------+------------------------+

但是正如您所看到的，该距离与正确的id字段不对应，应该是1953年的id，而是1960年的。

我将如何继续进行纠正？

PS;如果您对其他主题/问题感兴趣； select non duplicates by column from select query

Answer 1

MySql 8兼容

WITH dist as (
SELECT b.id, b.type, b.x, b.y, b.z, 
    SQRT(POWER(ABS(1654.5413 - b.x), 2) + POWER(ABS(-2293.7571 - b.y), 2) + POWER(ABS(-1.1996 - b.z), 2)) AS "distance" 
        FROM businesses b 
)
select * from dist d1
where distance = (
select  min(distance)
from dist d2
  where d1.type = d2.type
)

对于Mysql 8 <，您可以考虑为查询创建视图，例如

CREATE VIEW DIST AS (
  SELECT b.id, b.type, b.x, b.y, b.z, 
    SQRT(POWER(ABS(1654.5413 - b.x), 2) + POWER(ABS(-2293.7571 - b.y), 2) + POWER(ABS(-1.1996 - b.z), 2)) AS "distance" 
        FROM businesses b 
)

然后

select * from dist d1
where distance = (
select  min(distance)
from dist d2
  where d1.type = d2.type
)

Answer 2

只需要一个hading子句

SELECT id,type, distance AS 'minDistance'
FROM(
SELECT id, type, distance FROM (SELECT b.id, b.type, b.x, b.y, b.z, 
    SQRT(POWER(ABS(1654.5413 - b.x), 2) + POWER(ABS(-2293.7571 - b.y), 2) + POWER(ABS(-1.1996 - b.z), 2)) AS "distance" 
        FROM businesses b ORDER BY distance ASC) as T) AS TABLE
GROUP BY type having distance=min(distance) -- added
ORDER BY 'minDistance'

按列选择非重复项，字段不对应

2 个答案: