Question

我的表： vocabulary

    id          word
--------------------------
    1           hello
    2           hello
    3           how
    4           how
    5           how
    6           are
    7           hello
    8           hello
    9           are
    10          are
    11          are
    12          are
    13          hello

我想要select id from vocabulary where id=$id and {all rows that are both the same word and adjacent}

注意：我想要他们两个：[id = $ id]和[所有相同的单词和相邻的行]

事实上，我需要SELECT查询来执行以下操作：（三个示例）

$id=1，结果： 1,2 // [1 $id=1] - [2代表1和2相同且相邻]
$id=6，结果： 6 // [6 $id=6]
$id=10，结果： 9,10,11,12 // [10 $id=10] - [9,11,12代表10的字是与9,11,12相同

Answer 1

这是一个基本模式，你可以适应你的目的......

DROP TABLE IF EXISTS my_table;

CREATE TABLE my_table
(id INT NOT NULL AUTO_INCREMENT PRIMARY KEY
,word VARCHAR(12) NOT NULL
);

INSERT INTO my_table VALUES
(1 ,'hello'),
(2 ,'hello'),
(3 ,'how'),
(4 ,'how'),
(5 ,'how'),
(6 ,'are'),
(7 ,'hello'),
(8 ,'hello'),
(9 ,'are'),
(10,'are'),
(11,'are'),
(12,'are'),
(13,'hello');

SELECT a.id start
     , MIN(c.id) end 
  FROM my_table a
  LEFT 
  JOIN my_table b 
    ON b.id = a.id - 1
   AND b.word = a.word
  LEFT 
  JOIN my_table c 
    ON c.id >= a.id
   AND c.word = a.word
  LEFT 
  JOIN my_table d 
    ON d.id = c.id + 1
   AND d.word = a.word
 WHERE b.id IS NULL 
   AND c.id IS NOT NULL
   AND d.id IS NULL
 GROUP 
    BY a.id; 

+-------+------+
| start | end  |
+-------+------+
|     1 |    2 |
|     3 |    5 |
|     6 |    6 |
|     7 |    8 |
|     9 |   12 |
|    13 |   13 |
+-------+------+

正如McAdam331所暗示的，扩展这一想法的一种方法如下：

SELECT *  
  FROM vocabulary 
  JOIN tmpTable 
 WHERE id BETWEEN tmpTable.start AND tmpTable.end 
  AND tmpTable.start = $id;

Answer 2

这是一个使用变量的解决方案：

SELECT id, word
FROM (
  SELECT id,       
         @rnk:= CASE WHEN @word = word THEN @rnk 
                   ELSE @rnk + 1
              END AS rnk,
         @word:= word AS word
  FROM vocabulary, (SELECT @rnk:=0) as vars    
  ORDER BY id ) s
WHERE s.rnk = (
    SELECT rnk
    FROM (
      SELECT id,       
             @r:= CASE WHEN @w = word THEN @r 
                       ELSE @r + 1
                  END AS rnk,
             @w:= word AS word
      FROM vocabulary, (SELECT @r:=0) as vars    
      ORDER BY id ) t
    WHERE id = 10) -- 10 is equal to $id

SQL Fiddle Demo

由于MySQL中缺少CTE，相同的查询重复两次。 @rnk和@r变量用于标识word表中vocabulary个值的连续岛屿。

第二个查询选择岛屿值（例如@r = 5为id = 10），第一个使用此值选择属于同一岛屿的所有记录。

如何选择MySQL中的相邻列

2 个答案: