Can I randomly select a row from one table and use a static identifier to select corresponding data in another table?

Question

The following script was initially intended to select a row at random, which it could do fine, however, I an unable to figure out how to amend it to select data from a second table using a column ID called "nid" which is the same in both tables:

    $conn = mysqli_connect($host,$username,$password, $database) or die(mysql_error ()); 


$total_rows = 5;
$selected_row = mt_rand(0, $total_rows);


$query="SELECT * FROM `node` LIMIT $selected_row, 1;";
$result=$conn->query($query);

while($row = $result->fetch_assoc()) {
$node=$row["nid"];
echo $row["title"];

$query2="SELECT * FROM `field_data_body` LIMIT $node, 1;";
$result2=$conn->query($query2);

while($row = $result->fetch_assoc()) {
echo $row["body_value"];

 }

Admittedly, the above is not really close to working, but I was hardpressed to find an example of what I was after.

These tables are in the database for a Drupal site, so the title field and the body_value fields are in two different tables; ultimately, I would like to echo a result that is a matching set of title and body_value for a randomly selected node.

Speaking of this script specifically, I want to use the nid to find the corresponding row for the second table.

Is this possible?

The bit that works, selecting the data I want from a single table is in the following format:

    $total_rows = 5;
$selected_row = mt_rand(0, $total_rows);


$query="SELECT * FROM `field_data_body` LIMIT $selected_row, 1;";
$result=$conn->query($query);

while($row = $result->fetch_assoc()) {
echo $row["body_value"];

 }
?>

UPDATE:

At the suggestion of a commenter, I used a join, and ended up with:

$conn = mysqli_connect($host,$username,$password, $database) or die(mysql_error ()); 


$total_rows = 5;
$selected_row = mt_rand(0, $total_rows);

//Use the result in your limit.
$query="SELECT a.nid, a.title, b.entity_id, b.body_value
FROM node a, field_data_body b
WHERE a.nid = b.entity_id LIMIT $selected_row, 1;";
$result=$conn->query($query);

while($row = $result->fetch_assoc()) {
echo $row["title"];
echo " | ";
echo $row["body_value"];

 }

which worked perfectly.

Answer 1

for future reference since you have solved your problem, you need to close the previous connection before starting a new one, or free the results

$conn = mysqli_connect($host,$username,$password, $database) or die(mysql_error ()); 


$total_rows = 5;
$selected_row = mt_rand(0, $total_rows);


$query="SELECT * FROM `node` LIMIT $selected_row, 1;";
$result=$conn->query($query);

while($row = $result->fetch_assoc()) {
$node=$row["nid"];
echo $row["title"];
$result->close(); // close $result

$query2="SELECT * FROM `field_data_body` LIMIT $node, 1;";
$result2=$conn->query($query2);

while($row = $result->fetch_assoc()) {
echo $row["body_value"];
 }
$result2->close(); // close $result2

i also notice you haven't closed the connection on the UPDATE you posted either which will lead you to run into the same problem again later on.

Answer 2

如果这只是选择一条记录，则不必定义LIMIT，而是可以在WHERE中使用随机生成的值来选择该行！

Answer 3

You can just join the two tables. Beside that, your code has a potential problem. It relies on the existence of at least 5 records. You can avoid that by putting the randomization into the query. The code will then be

$conn = mysqli_connect($host,$username,$password, $database) or die(mysql_error()); 

$query  = "SELECT n.*, b.* FROM `node` AS n LEFT JOIN `field_data_body` AS b ON n.nid=b.nid ORDER BY REVERSE(RAND()) LIMIT 0, 1;";
$result = $conn->query($query);
$row    = $result->fetch_assoc();
$result->close();

echo $row["title"];
echo $row["body_value"];

The REVERSE() function makes the result from RAND() more random. You may omit it, if you want.