if exists - syntax query

[sheepsheep]

I need to check if a record exists, and depending on whether the outcome is true or false carry out one or another queries.

Check tblResults to see if there is a record which has $DateLogRef and $MachineRef - if it is true do 'x' - if false do 'y'.

I am going round in circles trying to get the syntax right, I only get error messages saying things like
Parse error: syntax error, unexpected T_STRING, expecting '(' in /readings/process_readings.php on line 177 -which is IF Exists ($DateLogRef, $MachineRef) - , I don't get as far as any other type of error message to say whether the code actually does what I want it to....

Any help in getting the syntax write first of all would be appreciated, plus any general advice on Exists would be fantastic as this is all new to me.

code I have so far

$query = "SELECT `DateLogRef`, `MachineRef` FROM `tblResults` WHERE ClientRef=$ClientRef";
$result94 = mysql_query($query) 
    or die (mysql_error()); 
while ($row94 = mysql_fetch_array($result94))
{
$DateLogRef = "row94[0]";
$MachineRef = "row94[1]";

IF Exists ($DateLogRef, $MachineRef) 
   {     "UPDATE tblResults 
        SET BC = $BValue, CC = $CValue
        WHERE DateLog = $DateLogRef
             AND MachineId = $MachineRef
             AND ConcesRef = $ConcesRef";
			 }
ELSE
  {
        "INSERT INTO tblResults (DateLogRef,MachineRef,ConcesRef,BC,CC,LoadedBy)
        VALUES ('$DateLogRef','$MachineId','$ConcesRef','$BC','$CC','$UserId')";
		}

} // end while

[laserlight]

see if there is a record which has $DateLogRef and $MachineRef

What do you mean by this? The problem is that an "exists" construct does not exist in PHP, and it is unclear as to what you are trying to do.

[Piranha]

Exists is not a built-in function, so I guess that you have built and tested it yourself. Anyway if-statements should be inside paranthesis:

IF (Exists ($DateLogRef, $MachineRef)) 

I am curious about a few other things. What does this row do?

        "INSERT INTO tblResults (DateLogRef,MachineRef,ConcesRef,BC,CC,LoadedBy)
        VALUES ('$DateLogRef','$MachineId','$ConcesRef','$BC','$CC','$UserId')"; 

The normal way to handle strings is to insert them into a variable, and that is not done here.

[sheepsheep]

to try to explain a bit more and perhaps turn the question on its head

Quote:
see if there is a record which has $DateLogRef and $MachineRef

What do you mean by this? The problem is that an "exists" construct does not exist in PHP, and it is unclear as to what you are trying to do.

I want to query the mysql database to see if there is a record within tblResults that contains both the variables $DateLogRef and $MachineRef.

I had hoped that I had previously set these variables in the query

$query = "SELECT `DateLogRef`, `MachineRef` FROM `tblResults` WHERE ClientRef=$ClientRef"; 
$result94 = mysql_query($query) 
    or die (mysql_error()); 
while ($row94 = mysql_fetch_array($result94)) 
{ 
$DateLogRef = "row94[0]"; 
$MachineRef = "row94[1]"; 

If there is a record that contains both $DateLogRef and $MachineRef, then I want to update that record, if there isn't a record that contains both $DateLogRef and $MachineRef, then I want to create a new record........

Does this explain more about what I am trying to achieve?

Any pointers in the right direction would be greatfully received.

[laserlight]

I want to query the mysql database to see if there is a record within tblResults that contains both the variables $DateLogRef and $MachineRef.

hmm... then where does $ClientRef come into the picture? Your first statement queries the database for rows for which the ClientRef field is equal to $ClientRef. It then iterates over the result set. Unfortunately, $DateLogRef and $MachineRef are set to the strings "row94[0]" and "row94[1]" respectively, and have nothing to do with the result set.

It looks like there should be exactly one row for which the ClientRef field is equal to $ClientRef, upon which we can write:

$query = "SELECT `DateLogRef`, `MachineRef` FROM `tblResults` WHERE ClientRef=$ClientRef";
$result = mysql_query($query)
    or die (mysql_error());
$row = mysql_fetch_assoc($result);
$DateLogRef = $row['DateLogRef'];
$MachineRef = $row['MachineRef'];

But now we get to the part that I do not understand. So far there has been only one table involved. So, the row that matches $DateLogRef and $MachineRef is the same one that matches $ClientRef. This means that $DateLogRef and $MachineRef are redundant.

Your code would then be something like:

// Check to see if the row already exists.
$query = "SELECT COUNT(*) FROM tblResults WHERE ClientRef=$ClientRef";
$result = mysql_query($query)
    OR die(mysql_error());
$row_count = mysql_result($result, 0);
if ($row_count == 1)
{
    // Row exists, so update it.
    $query = "UPDATE tblResults
        SET BC=$BValue, CC=$CValue
        WHERE ClientRef=$ClientRef";
}
else
{
    // insert row
}
mysql_query($query);