multi query select using wrong array? - php

Question

I have a multi query select which half works. The first query is straight forward.
$sql = "SELECT riskAudDate, riskClientId, RiskNewId FROM tblriskregister ORDER BY riskId DESC LIMIT 1;";
The second one doesn't seem to work even when I do it on its own:
$sql ="SELECT LAST(riskFacility) FROM tbleClients";
If I get rid of the LAST it returns the first entry in that field of the table. I want to use the LAST to get the LAST entry in that field.
When I do the first query on its own I get the data returned and I can echo it to the screen. When I add the second (with out the LAST) I get nothing. Here is what I am using
$result = $conn->query($sql);
if ($result == TRUE){
$r = $result->fetch_array(MYSQLI_ASSOC);
echo $r['riskAudDate'];
echo $r['riskClientId'];
echo $r['RiskNewId'];
echo $r['riskFacility'];
echo "<pre>";
print_r($r);
echo "</pre>";
}
The last bit is just for me to see whats in the array and just for testing.
So I have worked out that its the results array that is not right.
If I change the actual query to multi query I get this:
Call to a member function fetch_array() on boolean
So the array bit seems to be wrong for a multi query. The data returned is one row from each table. It works for the top query but add in the second (which I'm not sure is correct anyway) and the whole things crashes. So I guess it's a two part question. Whats wrong with my inserts and whats wrong with my returned array?

Answer 1

There is no last() function in mysql, it is only supported in ms access, if I'm not much mistaken. In mysql you can do what you do in the 1st query: do an order by and limit the results to 1.
According to the error message, the $conn->query($sql) returns a boolean value (probably true), therefore you cannot call $result->fetch_array(MYSQLI_ASSOC) on it. Since we have no idea what exactly you have in $sql variable, al I can say is that you need to debug your code to detrmine why $conn->query($sql) returns a boolean value.
Although it is not that clear from mysqli_query()'s documentation, but it only supports the execution of 1 query at a time. To execute multiple queries in one go, use mysqli_multi_query() (you can call this one in OO mode as well, see documentation). However, for security reasons I would rather call mysqli_query() twice separately. It is more difficult to execute a successful sql injection attack, if you cannot execute multiple queries.

Answer 2

It seems to me you are trying to do two SQL-queries at once.
That is not possible. Do a separate
$result = $conn->query($sql);
if ($result == TRUE){
while( $r = $result->fetch_array(MYSQLI_ASSOC)) {
...
}
}
for each SQL-query.
concerning :
$sql ="SELECT LAST(riskFacility) FROM tbleClients";
since the last function does not exists in MySQL i would recommend doing a sort like this(because i don't know what you mean with last )
$sql ="SELECT riskFacility FROM tbleClients order by riskFacility desc limit 0,1";