SELECT N rows before and after the row matching the condition? - mysql

Question

The behaviour I want to replicate is like grep with -A and -B flags .
eg grep -A 2 -B 2 "hello" myfile.txt will give me all the lines which have "hello" in them, but also 2 lines before and 2 lines after it.
Lets assume this table schema :
+--------+-------------------------+
| id | message |
+--------+-------------------------+
| 1 | One tow three |
| 2 | No error in this |
| 3 | My testing message |
| 4 | php module test |
| 5 | hello world |
| 6 | team spirit |
| 7 | puzzle game |
| 8 | social game |
| 9 | stackoverflow |
|10 | stackexchange |
+------------+---------------------+
Now a query like :
Select * from theTable where message like '%hello%' will result in :
5 | hello world
How can I put another parameter "N" which selects N rows before, and N rows after the matched record i.e. for N = 2, the result should be :
| 3 | My testing message |
| 4 | php module test |
| 5 | hello world |
| 6 | team spirit |
| 7 | puzzle game |
For simplicity assume 'like %TERM%' matches only 1 row .
Here the result is supposed to be sorted on auto-increment id field.

Answer 1

Right, this works for me:
SELECT child.*
FROM stack as child,
(SELECT idstack FROM stack WHERE message LIKE '%hello%') as parent
WHERE child.idstack BETWEEN parent.idstack-2 AND parent.idstack+2;

Answer 2

Don't know if this is at all valid MySQL but how about
SELECT t.*
FROM theTable t
INNER JOIN (
SELECT id FROM theTable where message like '%hello%'
) id ON id.id <= t.id
ORDER BY
ID DESC
LIMIT 3
UNION ALL
SELECT t.*
FROM theTable t
INNER JOIN (
SELECT id FROM theTable where message like '%hello%'
) id ON id.id > t.id
ORDER BY
ID
LIMIT 2

Answer 3

Try this simple one (edited) -
CREATE TABLE messages(
id INT(11) DEFAULT NULL,
message VARCHAR(255) DEFAULT NULL
);
INSERT INTO messages VALUES
(1, 'One tow three'),
(2, 'No error in this'),
(3, 'My testing message'),
(4, 'php module test'),
(5, 'hello world'),
(6, 'team spirit'),
(7, 'puzzle game'),
(8, 'social game'),
(9, 'stackoverflow'),
(10, 'stackexchange');
SET #text = 'hello world';
SELECT id, message FROM (
SELECT m.*, #n1:=#n1 + 1 num, #n2:=IF(message = #text, #n1, #n2) pos
FROM messages m, (SELECT #n1:=0, #n2:=0) n ORDER BY m.id
) t
WHERE #n2 >= num - 2 AND #n2 <= num + 2;
+------+--------------------+
| id | message |
+------+--------------------+
| 3 | My testing message |
| 4 | php module test |
| 5 | hello world |
| 6 | team spirit |
| 7 | puzzle game |
+------+--------------------+
N value can be specified as user variable; currently it is - '2'.
This query works with row numbers, and this guarantees that the nearest records will be returned.

Answer 4

Try
Select * from theTable
Where id >=
(Select id - variableHere from theTable where message like '%hello%')
Order by id
Limit (variableHere * 2) + 1

Answer 5

(MS SQL Server only)
The most reliable way would be to use the row_number function that way it doesn't matter if there are gaps in the id. This will also work if there are multiple occurances of the search result and properly return two above and below each result.
WITH
srt AS (
SELECT ROW_NUMBER() OVER (ORDER BY id) AS int_row, [id]
FROM theTable
),
result AS (
SELECT int_row - 2 AS int_bottom, int_row + 2 AS int_top
FROM theTable
INNER JOIN srt
ON theTable.id = srt.id
WHERE ([message] like '%hello%')
)
SELECT theTable.[id], theTable.[message]
FROM theTable
INNER JOIN srt
ON theTable.id = srt.id
INNER JOIN result
ON srt.int_row >= result.int_bottom
AND srt.int_row <= result.int_top
ORDER BY srt.int_row

Answer 6

Adding an answer using date instead of an id.
The use-case here is an on-call rotation table with one record pr week.
Due to edits the id might be out of order for the purpose intended.
Any use-case having several records pr week, pr date or other will of course have to be mended.
+----------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| startdate| datetime | NO | | NULL | |
| person | int(11) | YES | MUL | NULL | |
+----------+--------------+------+-----+---------+----------------+
The query:
SELECT child.*
FROM rota-table as child,
(SELECT startdate
FROM rota-table
WHERE YEARWEEK(startdate, 3) = YEARWEEK(now(), 3) ) as parent
WHERE
YEARWEEK(child.startdate, 3) >= YEARWEEK(NOW() - INTERVAL 25 WEEK, 3)
AND YEARWEEK(child.startdate, 3) <= YEARWEEK(NOW() + INTERVAL 25 WEEK, 3)