Use Query Result Row in Another Query

Question

I'm trying to use the row from a query in another query.

This query correctly displays the username of the user currently signed in:

$param = $fgmembersite->UserEmail();

$query = mysqli_query($con, "SELECT username FROM Users1 WHERE email = '$param'
");

while ($row = mysqli_fetch_array($query)){
echo $row['username'] ;
    }

I'm trying to find a way to use $row['username'] in another query something like...

$sql = mysqli_query($con, "SELECT * FROM messages WHERE to_user = '" . $row['username'] . "' ");

This doesn't give me a coding error, but it doesn't work. The username row obviously can't be taken from a separate query the way I'm attempting.

I have tried every combination I can think of but nothing has worked for me. Any help greatly appreciated.

Jaycee · Accepted Answer · 2013-09-13 22:13:31Z

1

Try a subquery

SELECT * FROM messages WHERE to_user in (SELECT username FROM Users1 WHERE email = '$param')

answered Sep 13, 2013 at 22:13

Jaycee

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Comments

Jonathan Kuhn · Accepted Answer · 2013-09-13 22:14:54Z

1

You can join the queries into one:

SELECT `messages`.*
FROM `messages`
    JOIN `Users1`
        ON `Users1`.`username`=`messages`.`to_user`
WHERE
    `Users1`.`email`='$param'

answered Sep 13, 2013 at 22:14

Jonathan Kuhn

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Comments

MKB · Accepted Answer · 2013-09-13 22:16:51Z

1

Well you should place your second query inside while:

while ($row = mysqli_fetch_array($query)){
  echo $row['username'] ;
  $sql = mysqli_query($con, "SELECT * FROM messages WHERE to_user = 
    '" . $row['username'] . "' ");
}

Now loop ends when mysqli_fetch_arrray returns NULL and that NULL you are trying to insert into second query.

answered Sep 13, 2013 at 22:16

MKB

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Comments

Goontracker · Accepted Answer · 2013-09-13 22:14:30Z

0

You can combine the two queries into one.

SELECT * FROM messages WHERE to_user = (SELECT username FROM Users1 WHERE email = '$param')

answered Sep 13, 2013 at 22:14

Goontracker

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