<?php
echo "<body style=\"background-color: #FF8000\">";
?> 
<form name="textsuche" method="post" 
action="<?php echo $_SERVER['PHP_SELF']; ?>">
<pre>
id:               <INPUT TYPE="text" MAXLENGTH="30" SIZE="15" NAME="id">
Bauteil:          <INPUT TYPE="text" MAXLENGTH="30" SIZE="15" NAME="bauteil">
Etage:            <INPUT TYPE="text" MAXLENGTH="30" SIZE="15" NAME="etage">
Raumnummer1:      <INPUT TYPE="text" MAXLENGTH="30" SIZE="15" NAME="raum1">
Raumnummer2:      <INPUT TYPE="text" MAXLENGTH="30" SIZE="15" NAME="raum2">
Bezeichnung:      <INPUT TYPE="text" MAXLENGTH="30" SIZE="15" NAME="bez">
Fläche:           <INPUT TYPE="text" MAXLENGTH="30" SIZE="15" NAME="flaeche">
Gesamthöhe:       <INPUT TYPE="text" MAXLENGTH="30" SIZE="15" NAME="hoehe">
Material Wand:    <INPUT TYPE="text" MAXLENGTH="30" SIZE="15" NAME="material">
Flächentyp:       <INPUT TYPE="text" MAXLENGTH="30" SIZE="15" NAME="typ">
Nutzer:           <INPUT TYPE="text" MAXLENGTH="30" SIZE="15" NAME="nutzer">
lh:               <INPUT TYPE="text" MAXLENGTH="30" SIZE="15" NAME="lh">
                  <INPUT TYPE="submit" VALUE="Suchen" name="submit"> <INPUT TYPE="Reset" VALUE="Zurücksetzen" name="submit">

</pre>
</form

<!DOCTYPE html>
<html>
<body>
<header>
<h1>
Suchergebnis</h1>
</header>

</html>



<?php


if (isset($_POST['submit'])) {
    print_r($_POST);   

$sql = "SELECT * FROM institut2;";
if(isset($_POST['id'])) { 
    $sql="SELECT * FROM institut2 WHERE id LIKE ".
        "'%". mysql_real_escape_string($_POST['id']) . "%'".
            " ";
} 

if(isset($_POST['bauteil'])) { 
    $sql="SELECT * FROM institut2 WHERE Bauteil LIKE ".
        "'%". mysql_real_escape_string($_POST['bauteil']) . "%'".
        " ";
} 


if(isset($_POST['etage'])) { 
    $sql="SELECT * FROM institut2 WHERE Etage LIKE ".
        "'%". mysql_real_escape_string($_POST['etage']) . "%'".
        " ";
} 


if(isset($_POST['raum1'])) { 
    $sql="SELECT * FROM institut2 WHERE Raumnummer1 LIKE ".
        "'%". mysql_real_escape_string($_POST['raum1']) . "%'".
        " ";
} 


if(isset($_POST['raum2'])) { 
    $sql="SELECT * FROM institut2 WHERE Raumnummer2 LIKE ".
        "'%". mysql_real_escape_string($_POST['raum2']) . "%'".
        " ";
} 
if(isset($_POST['bez'])) { 
    $sql="SELECT * FROM institut2 WHERE Bezeichnung LIKE ".
        "'%". mysql_real_escape_string($_POST['bez']) . "%'".
        " ";
} 
if(isset($_POST['flaeche'])) { 
    $sql="SELECT * FROM institut2 WHERE Fläche LIKE ".
        "'%". mysql_real_escape_string($_POST['flaeche']) . "%'".
        " ";
} 
if(isset($_POST['hoehe'])) { 
    $sql="SELECT * FROM institut2 WHERE Gesamthöhe LIKE ".
        "'%". mysql_real_escape_string($_POST['hoehe']) . "%'".
        " ";
} 
if(isset($_POST['material'])) { 
    $sql="SELECT * FROM institut2 WHERE Material_Wand LIKE ".
        "'%". mysql_real_escape_string($_POST['material']) . "%'".
        " ";
}
if(isset($_POST['typ'])) { 
    $sql="SELECT * FROM institut2 WHERE Flächentyp LIKE ".
        "'%". mysql_real_escape_string($_POST['typ']) . "%'".
        " ";
} 
if(isset($_POST['nutzer'])) { 
    $sql="SELECT * FROM institut2 WHERE Nutzer LIKE ".
        "'%". mysql_real_escape_string($_POST['nutzer']) . "%'".
        "";
} 

if(isset($_POST['lh'])) { 
    $sql="SELECT * FROM institut2 WHERE lh LIKE ".
        "'%". mysql_real_escape_string($_POST['lh']) . "%'".
        " ";
} 
$c = mysql_connect('localhost', 'Julian', '123') or die("Keine Verbindung möglich. Benutzername oder Passwort sind falsch");
mysql_select_db('Institutgoe') or die("Die Datenbank existiert nicht.");

if(1==0) {
$sql =
"SELECT * FROM institut2 WHERE id = '%"
            . mysql_real_escape_string($_POST['id']) . "%'
         ";
"SELECT * FROM institut2 WHERE Bauteil = '%"
            . mysql_real_escape_string($_POST['bauteil']) . "%'
         ";      
"SELECT * FROM institut2 WHERE Etage = '%"
            . mysql_real_escape_string($_POST['etage']) . "%'
         ";
"SELECT * FROM institut2 WHERE Raumnummer1 = '%"
            . mysql_real_escape_string($_POST['raum1']) . "%'
         ";
"SELECT * FROM institut2 WHERE Raumnummer2 = '%"
            . mysql_real_escape_string($_POST['raum2']) . "%'
         ";
"SELECT * FROM institut2 WHERE Bezeichnung = '%"
            . mysql_real_escape_string($_POST['bez']) . "%'
         ";
"SELECT * FROM institut2 WHERE Fläche = '%"
            . mysql_real_escape_string($_POST['flaeche']) . "%'
         ";
"SELECT * FROM institut2 WHERE Gesamthöhe = '%"
            . mysql_real_escape_string($_POST['hoehe']) . "%'
         ";
"SELECT * FROM institut2 WHERE Material_Wand = '%"
            . mysql_real_escape_string($_POST['material']) . "%'
         ";
"SELECT * FROM institut2 WHERE Flächentyp = '%"
            . mysql_real_escape_string($_POST['typ']) . "%'
         ";
"SELECT * FROM institut2 WHERE lh = '%"
            . mysql_real_escape_string($_POST['nutzer']) . "%'
         ";
}
echo "<!-- SQL = $sql -->";
  $result = mysql_query($sql) or die(mysql_error());
 if(($treffer = mysql_num_rows($result)) > 1) {
 }

Der letzte Teil ist richtig.

...zur Antwort