read random lines from a record MySQL-PHP - php

Question

i will keep it simple to understand :
1) i have a database with 2 columns - word and text
2) Each word has approx. 600,000 lines of text associated with it.
3) Iam a .net person shifting to php and mysql - so a little knowledge.
MY requirement :
1) I will pass the word through a form
2) The form will connect to the database and should display 2000 random lines from those 600,000 which should be non-repetitive
My current progress :
<?php
$con = mysql_connect("localhost","text_minx","pwd");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
mysql_select_db("my_db", $con);
$result = mysql_query("SELECT * FROM Data
WHERE word='health'");
while($row = mysql_fetch_array($result))
{
echo $row['lines'];
echo "<br />";
}
?>
This shows all the lines. What i want is to read this $row['lines'] in a possible array and randomly select 2000 lines from it - and they should be non-repetitive.
Any help please?

Answer 1

Something like this:
$result = mysql_query("SELECT DISTINCT * FROM Data WHERE word='health' ORDER BY RAND() LIMIT 2000");
It's more efficient to select the 2000 random lines by MySQL instead of by PHP, as above.
Also note that SELECT DISTINCT will select only unique rows, which you should probably remove anyway. If you specify the column names instead of using * then you can choose which columns you want to be unique - although this also depends somewhat on how your table is built.

Answer 2

i think this is the way you want
SELECT * FROM Data
WHERE word='health' ORDER BY RAND() LIMIT 0,2000
this will give you 2000 records sorted by any random order

Answer 3

You need to split your row result into array (as it's currently a string), and then you can select 2000 lines randomly.
Assuming that the text has like breaks as line separators, it would look like that:
echo $row['lines']; //starts from this line of your code
$data = explode("\n", $row['lines']);
shuffle($data);
$random_lines = array_slice($data, 0, 2000);
This does not take care of non-repetition, though. If I understand your need correctly, you can use array_unique() function before passing it to shuffle().