mysql - 如何查询连通坐标？

Question

我有一个表，我在其中映射基于 X 和 Y 坐标的值(XY 是主键)

+---+---+--------+--------+
| X | Y | Data 1 | Data 2 |
+---+---+--------+--------+

假设我将这些值存储在那里:

    X →
    1234567
Y 1|XXXX  X|
↓ 2| XX   X|
  3|    X X|
  4| X   XX|
  5| X XXXX|

如何构建 SQL 查询以获取所有连接的值作为结果？获取顺序并不重要。

例如，如果我查询:

• X=3 和 Y=2 它获取:(1,1),(2,1),(3,1),(4 ,1),(2,2),(3,2)
• X=5 和 Y=3 它获取:(5,3)
• X=2 和 Y=4 它获取:(2,4),(2,5)
• X=7 和 Y=3 它获取:(4,5),(5,5),(6,4),(6 ,5),(7,1),(7,2),(7,3),(7,4),(7,5)

作为 SQL 的示例表:

DROP TABLE IF EXISTS `test`;
CREATE TABLE `test` (
  `x` int(11) NOT NULL,
  `y` int(11) NOT NULL,
  PRIMARY KEY (`x`,`y`)
);
INSERT INTO `test` VALUES
(1, 0),(1, 1),(2, 2),(2, 4),(2, 5),(3, 1),(3, 2),(4, 1),(4, 5),
(5, 0),(5, 5),(6, 4),(6, 5),(7, 1),(7, 2),(7, 3),(7, 4),(7, 5);

Answer 1

你问的可以通过普通表表达式实现。

我在此示例中使用的是 TSQL，但可以使用其他 SQL 方言构建类似的查询。

让我们首先从列出所有相邻单元格的 View 开始:

create view [dbo].[fromto] as
select
t1.x as x_from, 
t1.y as y_from,
t2.x as x_to,
t2.y as y_to
from test t1
join test t2 on t2.x = t1.x and t2.y = t1.y + 1
union
select
t1.x as x_from, 
t1.y as y_from,
t2.x as x_to,
t2.y as y_to
from test t1
join test t2 on t2.x = t1.x and t2.y = t1.y - 1
union
select
t1.x as x_from, 
t1.y as y_from,
t2.x as x_to,
t2.y as y_to
from test t1
join test t2 on t2.x = t1.x + 1 and t2.y = t1.y
union
select
t1.x as x_from, 
t1.y as y_from,
t2.x as x_to,
t2.y as y_to
from test t1
join test t2 on t2.x = t1.x - 1 and t2.y = t1.y

现在我们必须递归地遍历这个 View :

with walk (x_col_from, y_col_from, x_col_to, y_col_to, stack ) as(
select 
x_from, 
y_from, 
x_to, 
y_to, 
cast(concat('|',x_from ,',',y_from, '|', x_to, ',', y_to) as varchar)
from fromto
union all
select 
walk.x_col_from, 
walk.y_col_from, 
fromto.x_to, 
fromto.y_to,
cast(concat(walk.stack,'|',fromto.x_to,',',fromto.y_to) as varchar)
from fromto
join walk on walk.x_col_to = fromto.x_from and walk.y_col_to = fromto.y_from 
where CHARINDEX(cast(concat('|',fromto.x_to,',',fromto.y_to) as varchar), walk.stack) = 0
)
select * from walk 

堆栈字段用于内存我们已经访问过的单元格。它还给出了通过网格的路径。