Select 个相邻条目

Question

我有一个带有文字注释的 table。我的应用程序显示按 pinned_flag 然后 note_date 排序的条目：

id | note_text | note_date | pinned_flag
----------------------------------------
1  | note1     | 01/04/2021 |  1 
----------------------------------------
3  | note2     | 01/02/2021 |  1 
----------------------------------------
5  | note3     | 01/05/2021 |  0 
----------------------------------------
4  | note4     | 01/03/2021 |  0 
----------------------------------------
2  | note5     | 01/01/2021 |  0
----------------------------------------

我需要 select 在具有给定 ID 的记录下方 1 条记录和上方 1 条记录。（对于条目 5，结果将是 3 和 4）我可以使用哪些查询来执行此操作？

Answer 1

如果您的 SQLite 版本是 3.25.0+，您可以使用 ROW_NUMBER() window 函数：

WITH cte AS (
    SELECT *, ROW_NUMBER() OVER (ORDER BY pinned_flag DESC, note_date DESC) rn 
    FROM tablename
)
SELECT id, note_text, note_date, pinned_flag
FROM cte
WHERE (SELECT rn FROM cte WHERE id = 5) IN (rn - 1, rn + 1);

如果您不能使用 window 函数，但您的 SQLite 版本是 3.15.0+，您可以使用 UNION ALL 和 Row Values:

WITH cte AS (SELECT * FROM tablename WHERE id = 5)
SELECT * FROM (
  SELECT * FROM tablename
  WHERE (pinned_flag, note_date) > (SELECT pinned_flag, note_date FROM cte)
  ORDER BY pinned_flag, note_date LIMIT 1
)
UNION ALL
SELECT * FROM (
  SELECT * FROM tablename
  WHERE (pinned_flag, note_date) < (SELECT pinned_flag, note_date FROM cte)
  ORDER BY pinned_flag DESC, note_date DESC LIMIT 1
);

对于以前的版本：

WITH cte AS (SELECT * FROM tablename WHERE id = 5)
SELECT * FROM (
  SELECT * FROM tablename
  WHERE pinned_flag > (SELECT pinned_flag FROM cte)
     OR (pinned_flag = (SELECT pinned_flag FROM cte) AND note_date > (SELECT note_date FROM cte))
  ORDER BY pinned_flag, note_date LIMIT 1
)
UNION ALL
SELECT * FROM (
  SELECT * FROM tablename
  WHERE pinned_flag < (SELECT pinned_flag FROM cte)
     OR (pinned_flag = (SELECT pinned_flag FROM cte) AND note_date < (SELECT note_date FROM cte))
  ORDER BY pinned_flag DESC, note_date DESC LIMIT 1
);

参见demo。

Select 个相邻条目

Select neighboring entries

sqlite

union

common-table-expression

window-functions

android-sqlite