http://en.wikipedia.org/wiki/SQL_injection

CREATE TABLE t ( id TINYINT, title VARCHAR(10) );
INSERT INTO t (id, title) VALUES (1, ‘aaa’), (2, ‘bbb’), (3, ‘ccc’), (4, ‘ddd’), (5, ‘eee’);

(a) DO @sn := 0;
SELECT @sn:=@sn+1 sn, id, title FROM t GROUP BY id ORDER BY id desc;
| sn | id | title |
+——+——+——-+
| 1 | 5 | eee |
| 2 | 4 | ddd |
| 3 | 3 | ccc |
| 4 | 2 | bbb |
| 5 | 1 | aaa |

(b) DO @sn := 0;
SELECT @sn:=@sn+1 sn, id, title FROM t GROUP BY id HAVING sn=2 ORDER BY id desc;
| 2 | 2 | bbb |

(c) DO @sn := 0;
SELECT @sn:=@sn+1 sn, id, title FROM t HAVING sn=2 ORDER BY id desc;
| 3 | 4 | ddd |

I do not understand why (b) is not able to retain the same order of sn as in (a). I am assuming it is the ‘HAVING sn=2′ that is forcing (b) to reset the sort order. However, (c) is able to maintain the same sn order as in (a) even with ‘HAVING sn=2′ clause in it, although it is not using the ‘GROUP BY id’ anymore.

Is there a way I can retain the sn sort order in (b) same as in (a)?

| version() |
+———–+
| 5.0.51a |

Here’s my code, I hope someone finds it useful:

SELECT id, title, @a := id, ( SELECT id FROM art WHERE album = ‘$album’ AND id @a ORDER BY title ASC LIMIT 1 ) AS next_id FROM art WHERE album = ‘$album’ AND id = ‘$id’

I made up the follwing:

SELECT id, title, @a := title, ( SELECT id FROM table WHERE title < @a ORDER BY title DESC LIMIT 1 ) AS prev_id,
( SELECT id FROM table WHERE title > @a ORDER BY title ASC LIMIT 1 ) AS next_id

prev_id and next_id will hold the id of the previous and next record based on the sort criteria (title). If there is nothing before or after, then they will be empty…

Hope this helps…

SELECT id, title, @a := title, ( SELECT id FROM table WHERE title @a ORDER BY title ASC LIMIT 1 ) AS next_id

prev_id and next_id will hold the id of the previous and next record based on the sort criteria (title). If there is nothing before or after, then they will be empty…

Hope this helps…

ace

select * from mytable LIMIT 0,20

The Limit 0,20 will give you a listing of 20 entries starting from 0. So, 1-20 records would be displayed. If you keep record of the number where you started in the header or somewhere else, then this would work pretty easy for you.

select * from mytable LIMIT 30,20 – Start from 30 and given you the next 20 records.