出现错误“'字段列表'中的未知列'文本'”

Question

I am trying to insert text to my database table reqviews . But I get the error message:

Unknown column 'text' in 'field list' . I'm not sure what's wrong with my code. Please help

if (isset($_POST['combut'])) {
    $rqvcom = $_POST['rqvcom'];
    $rqid = (int)$_GET['rqid'];
    $conn->query("
        INSERT INTO reqviews (rqvrqid, rqvuserid, rqvcom, rqvdate)
            SELECT {$rqid}, {$sid}, {$rqvcom}, NOW()
            FROM requests
            WHERE EXISTS (
                SELECT rqid
                FROM requests
                WHERE rqid = {$rqid})
            AND NOT EXISTS (
                SELECT rqvid
                FROM reqviews
                WHERE rqvuserid = {$sid}
                AND rqvrqid = {$rqid})
            LIMIT 1
    ");
}

What my code does: When some text is typed into rqvcom textarea, that text gets iserted to rqvcom column on reqviews table. If a row already exists on reqviews table with a rqvuserid user, then another row with that same userid cannot be inserted. My problem is my code gives me the error message I provided.

Edit: Table reqviews

rqvid | rqvrqid | rqvuserid | rqvcom | rqvdate

Table requests

rqid

Answer 1

SELECT {$rqid}, {$sid}, {$rqvcom}, NOW()

This will select the column names that are in those variables:

// let's say these are the values in your variables:
$rqid = "text";
$sid = "session123";
$rqvcom = "example";

// then this query:
SELECT {$rqid}, {$sid}, {$rqvcom}, NOW()

// is the same as:
SELECT text, session123, example, NOW()

That is why you're getting that error. It is highly unlikely that this is what you want. I suspect that what you actually want is to select the columns rqid , sid and rqvcom :

SELECT rqid, sid, rqvcom, NOW()

Edit : Now that you've added your table structures, it seems more likely that you want to actually select the string values, in which case you need to wrap the variables in quotes like @Giacomo M suggested:

SELECT '{$rqid}', '{$sid}', '{$rqvcom}', NOW()

// which will become:
SELECT 'text', 'session123', 'example', NOW()

Then your database will not confuse the strings with column names.

Answer 2

If you're trying to insert the value of $rqvcom into the database, you need to put it in quotes, since it's a string. Otherwise, it's treated as a column name.

$conn->query("
    INSERT INTO reqviews (rqvrqid, rqvuserid, rqvcom, rqvdate)
        SELECT {$rqid}, {$sid}, '{$rqvcom}', NOW()
        FROM requests
        WHERE EXISTS (
            SELECT rqid
            FROM requests
            WHERE rqid = {$rqid})
        AND NOT EXISTS (
            SELECT rqvid
            FROM reqviews
            WHERE rqvuserid = {$sid}
            AND rqvrqid = {$rqid})
        LIMIT 1
");

However, this leaves you open to SQL injection, so you should use a prepared statement.

$stmt = $conn->prepare("
    INSERT INTO reqviews (rqvrqid, rqvuserid, rqvcom, rqvdate)
        SELECT ?, ?, ?, NOW()
        FROM requests
        WHERE EXISTS (
            SELECT rqid
            FROM requests
            WHERE rqid = ?)
        AND NOT EXISTS (
            SELECT rqvid
            FROM reqviews
            WHERE rqvuserid = ?
            AND rqvrqid = ?)
        LIMIT 1
");
$stmt->bind_param("iisiii", $rqid, $sid, $rqvcom, $rqid, $sid, $rqid);
$stmt->execute();