Question

I’m wondering what is command for database query that is querying data forward or back between rows? Just like forward and back button. Can someone give me an example? Thanks.

For examp:

$sql_xxxx = mysql_query("SELECT * FROM xxxx WHERE id='$xxx'") or die  (mysql_error());
$row_xxxx = mysql_fetch_array($sql_xxxx);

Now I need the two same query but for one forward and in the other backward the data.

Answer 1

Since you tagged PHP and MySQL I think I can guess what you are trying to do;

Usually you can control this with the ID of a record in MySQL, for example:

SELECT * FROM MYTABLE WHERE ID = 1;

In PHP, you can construct dynamic queries to get different results while just changing the value of a variable.

Lets say we now want to take the same query and make it dynamic:

$id = 1;
$query = "SELECT * FROM MYTABLE WHERE ID = $id ";

as long as you execute this query, it will give you the row with ID = 1 , cause now it is taking the value from the $id variable.

If you want the next row, then you execute the same query but now $id must have the next value.

$id = 2;

Having a “NEXT” and “BACK” button can be matter of just adding or substracting 1 to the $id variable.
Still, this is only an example. In most of the cases you should not play with id’s like that cause you should not assume that all id’s exist, remember that “DELETE” exist;

So you can try to execute better a little query to find the next value like this:

to go foward:

$query= "SELECT MIN(ID) FROM MYTABLE WHERE ID > $id"
// This will get you for sure the closest id next to the current one

and to go back:
$query= "SELECT MAX(ID) FROM MYTABLE WHERE ID < $id"

I hope this helps,

Regards