MySql variables and php - php

Question

I am getting an error with this in php. What is the correct way to format this string to pass to mysql_query() in php?
SELECT count(*) FROM agents INTO #AgentCount;
SELECT user_agent_parsed, user_agent_original, COUNT( user_agent_parsed ) AS thecount,
COUNT( * ) / ( #AgentCount) AS percentage
FROM agents
GROUP BY user_agent_parsed
ORDER BY thecount DESC LIMIT 50;
In php, here is how I set up the $query
$query = "
SELECT count(*) FROM agents INTO #AgentCount;
SELECT user_agent_parsed, user_agent_original, COUNT( user_agent_parsed ) AS thecount,
COUNT( * ) / ( #AgentCount) AS percentage
FROM agents
GROUP BY user_agent_parsed
ORDER BY thecount DESC LIMIT 50";
That exact query will work fine if I put it directly into MySql via a command line session. Do I need to issue two separate php calls to mysql_query() and store the first result?
I am getting the below error:
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'SELECT user_agent_parsed, user_agent_original, COUNT( user_agent_parsed ) AS thecount' at line 3
The reason for not using a sub select and instead choosing a MySql variable is to avoid a count() happening on every percentage calculation. Though it may be possible the engine is optimizing for that. So far, I have not been able to confirm that. I have also heard sub selects are almost always non optimal.
EXPLAIN tells me this:
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY agents index NULL user_agent_parsed 28 NULL 82900 Using temporary; Using filesort
2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Select tables optimized away

Answer 1

You can only have one query at a time in PHP.
$query1 = "SELECT count(*) FROM agents INTO #AgentCount"
$query2="
SELECT user_agent_parsed, user_agent_original, COUNT( user_agent_parsed ) AS thecount,
COUNT( * ) / ( #AgentCount) AS percentage
FROM agents
GROUP BY user_agent_parsed
ORDER BY thecount DESC LIMIT 50";
UPDATE
I have a DAL that contains all my queries. A typical function in my DAL looks like this:
// These functions are reusable
public function getAllRows($table)
{
$sql =" SELECT * FROM $table";
$this->query($sql);
return $this->query_result;
}
Then in my BLL (Business Layer) I have the following:
public function getUserAgents()
{
$result = parent::getAllRows();
$row = mysql_fetch_array($result);
return $row[0]; // Retrieves the first row
// Then you take this value and to a second request. Then return the answer / rows.
}

Answer 2

If you are using mysql_query, then yes, you need to send each query separately. From the description at the top of mysql_query's entry in the PHP manual: "mysql_query() sends a unique query (multiple queries are not supported) to the currently active database..."
As for subqueries, you'd be surprised; the query optimizer generally handles them very well.