MySql - 如何获取上一行的值和下一行的值？ [复制]

Question

我有下表，名为Example：

id(int 11) //not autoincriment
value (varchar 100)

它有以下几行数据：

0  100
2  150
3  200
6  250
7  300

请注意，id 值不是连续的。

到目前为止，我已经编写了这个 SQL：

SELECT * FROM Example WHERE id = 3

但是，我不知道如何获取上一个id 的值和下一个id 的值...

如果id = 3，请帮我获取上一个值和下一个值？

P.S.：在我的示例中，它将是：上一个 - 150，下一个 - 250。

Answer 1

一种解决方案是使用临时变量：

select 
    @prev as previous,
    e.id,
    @prev := e.value as current
from
    (
        select
            @prev := null
    ) as i,
    example as e
order by
    e.id

要获得“下一个”值，请重复该过程。这是一个例子：

select 
  id, previous, current, next
from
  (
    select
      @next as next,
      @next := current as current,
      previous,
      id
    from
      (
        select @next := null
      ) as init,
      (
        select
          @prev as previous,
          @prev := e.value as current,
          e.id
        from
          (
            select @prev := null
          ) as init,
          example as e
        order by e.id
      ) as a
    order by
      a.id desc
  ) as b
order by
  id

查看the example on SQL Fiddle

可能有点矫枉过正，但它可能会帮助你

Answer 2

选择下面的下一行：

SELECT * FROM Example WHERE id < 3 ORDER BY id DESC LIMIT 1

选择上面的下一行：

SELECT * FROM Example WHERE id > 3 ORDER BY id LIMIT 1

在一个查询中同时选择两者，例如使用UNION:

(SELECT * FROM Example WHERE id < 3 ORDER BY id DESC LIMIT 1)
 UNION
(SELECT * FROM Example WHERE id > 3 ORDER BY id LIMIT 1)

你的意思是？

Answer 3

SELECT *,
       (SELECT value FROM example e1 WHERE e1.id < e.id ORDER BY id DESC LIMIT 1 OFFSET 0) as prev_value,
       (SELECT value FROM example e2 WHERE e2.id > e.id ORDER BY id ASC LIMIT 1 OFFSET 0) as next_value
FROM example e
WHERE id=3;

如果您想为所选记录中的下一个和上一个值选择具有更高偏移量的记录，您可以在 OFFSET 关键字之后放置您自己的偏移量。

Answer 4

我的解决方案可能适合你：

SELECT * FROM Example
WHERE id IN (
(SELECT MIN(id) FROM Example WHERE id > 3),(SELECT MAX(id) FROM Example WHERE id < 3)
)

演示：http://sqlfiddle.com/#!9/36c1d/2

Answer 5

请试试这个sqlFiddle

SELECT value,
       (SELECT value FROM example e2
        WHERE e2.value < e1.value
        ORDER BY value DESC LIMIT 1) as previous_value,
       (SELECT value FROM example e3
        WHERE e3.value > e1.value
        ORDER BY value ASC LIMIT 1) as next_value
FROM example e1
WHERE id = 3

编辑：OP 提到在其中一个 cmets 中获取前一个 id 的值和下一个 id 的值，所以代码在这里 SQLFiddle

SELECT value,
      (SELECT value FROM example e2
       WHERE e2.id < e1.id
       ORDER BY id DESC LIMIT 1) as previous_value,
      (SELECT value FROM example e3
       WHERE e3.id > e1.id
       ORDER BY id ASC LIMIT 1) as next_value
FROM example e1
WHERE id = 3

Answer 6

一个可能的解决方案，如果你需要它在一行中

SELECT t.id, t.value, prev_id, p.value prev_value, next_id, n.value next_value
  FROM
(
  SELECT t.id, t.value,
  (
    SELECT id
      FROM table1
     WHERE id < t.id
     ORDER BY id DESC
     LIMIT 1
  ) prev_id,
  (
    SELECT id
      FROM table1
     WHERE id > t.id
     ORDER BY id
     LIMIT 1
  ) next_id
    FROM table1 t
   WHERE t.id = 3
) t LEFT JOIN table1 p
     ON t.prev_id = p.id LEFT JOIN table1 n
     ON t.next_id = n.id 

样本输出：

|身份证 |价值 | PREV_ID | PREV_VALUE |下一个 ID | NEXT_VALUE | |----|-------|---------|------------|---------|--- ---------| | 3 | 200 | 2 | 150 | 4 | 250 |

这里是SQLFiddle演示

Answer 7

如果您没有 ID，这对我有用。

下一步：

SELECT * FROM table_name
WHERE column_name > current_column_data
ORDER BY column_name ASC
LIMIT 1

上一个：

SELECT * FROM table_name
WHERE column_name < current_column_data
ORDER BY column_name DESC
LIMIT 1

我将其用于成员列表，其中搜索是在成员的姓氏上。只要您有当前记录中的数据，它就可以正常工作。

Answer 8

此查询使用用户定义的变量来计算与目标 id 的距离，并使用一系列包装查询来获得您想要的结果。桌子上只有一次传球，所以它应该表现良好。

select * from (
    select id, value from (
        select *, (@x := ifnull(@x, 0) + if(id > 3, -1, 1)) row from (
            select * from mytable order by id
        ) x 
    ) y
    order by row desc
    limit 3
) z
order by id

查看SQLFiddle

如果您不关心最后的行顺序，您可以省略最外层的包装查询。