The order the records are returned is not guaranteed unless you
specify an ORDER BY. You could run the same query multiple times and
the order the records are returned could be different each time.
Although this is rarely the case, especially with caching enabled.
Always do an ORDER BY with pagination, and make sure what you are
ordering by is unique. This is simple to do, just add the unique ID
field as the last order by field. Then you will always get
"consecutive" rows.
Brent
On Nov 23, 2009, at 12:09 PM, Miguel Cardenas wrote:
Hello list :)
I am developing an application that will show records in paginated
documents, i.e. 10 records per page
Lets supose this row structure
MyTable
ID(autoincrement) SectionID Name Description
The ID is automatic autoincrement for unique records, the SectionID
is to
separate items into different sections.
If I query a particular SectionID rows it should return all those
rows.
If I use "LIMIT x,10" it should return 10 rows beginning at record
#x, but
my doubt is:
Does the OFFSET x assumes its value to be #x number of consecutive
rows, or
it is relative to the query results?
For example
ID SID name description
------------------------------------------
01 01 nameA descriptionA
02 02 nameB descriptionB
03 01 nameC descriptionC
04 02 nameD descriptionD
05 02 nameE descriptionE
06 01 nameF descriptionF
07 02 nameG descriptionG
08 01 nameH descriptionH
09 02 nameI descriptionI
10 02 nameJ descriptionJ
------------------------------------------
If I do
SELECT name from MyTable SID where SID='02' LIMIT 1,2 (offset 1, 2
elements)
it should return: nameB, nameD
theni f I do
SELECT name from MyTable SID where SID='02' LIMIT 3,2 (offset 3, 2
elements)
it should return: nameE, nameG
and if I do
SELECT name from MyTable SID where SID='02' LIMIT 3,2 (offset 5, 2
elements)
it should return: nameI, nameJ
Is it correct? My doubt is if the OFFSET is relative to the SELECT
results
(to ignore the # first result rows) that match the condition
SID='02' only,
to show 2 by 2 records (or N by N)...
Thanks for your help
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