Combining queries for speed - php

Question

I started using only 1 query but then I wanted some to show up more than others so I ended up doing more queries but it, really slows down the load time, is there a way I can do them all in a single query but have them all with their separate variable name?
$sql23 = "SELECT * FROM monsters WHERE rare='0' AND level<='".$row['level']."' ORDER BY RAND() LIMIT 1;";
$result23 = mysqli_query($link,$sql23) or die(mysqli_error());
$battle_get23 = mysqli_fetch_array($result23);
$boss = "SELECT * FROM monsters WHERE rare='1' AND level<='".$row['level']."' ORDER BY RAND() LIMIT 1;";
$boss = mysqli_query($link,$boss) or die(mysqli_error());
$boss = mysqli_fetch_array($boss);
$rare1 = "SELECT * FROM monsters WHERE rare='2' AND level<='".$row['level']."' ORDER BY RAND() LIMIT 1;";
$rare1 = mysqli_query($link,$rare1) or die(mysqli_error());
$rare1 = mysqli_fetch_array($rare1);
$rare2 = "SELECT * FROM monsters WHERE rare='3' AND level<='".$row['level']."' ORDER BY RAND() LIMIT 1;";
$rare2 = mysqli_query($link,$rare2) or die(mysqli_error());
$rare2 = mysqli_fetch_array($rare2);
$rare3 = "SELECT * FROM monsters WHERE rare='4' AND level<='".$row['level']."' ORDER BY RAND() LIMIT 1;";
$rare3 = mysqli_query($link,$rare3) or die(mysqli_error());
$rare3 = mysqli_fetch_array($rare3);
$rare4 = "SELECT * FROM monsters WHERE rare='5' AND level<='".$row['level']."' ORDER BY RAND() LIMIT 1;";
$rare4 = mysqli_query($link,$rare4) or die(mysqli_error());
$rare4 = mysqli_fetch_array($rare4);
$rare5 = "SELECT * FROM monsters WHERE rare='6' AND level<='".$row['level']."' ORDER BY RAND() LIMIT 1;";
$rare5 = mysqli_query($link,$rare5) or die(mysqli_error());
$rare5 = mysqli_fetch_array($rare5);
$rare6 = "SELECT * FROM monsters WHERE rare='7' AND level<='".$row['level']."' ORDER BY RAND() LIMIT 1;";
$rare6 = mysqli_query($link,$rare6) or die(mysqli_error());
$rare6 = mysqli_fetch_array($rare6);
$rare7 = "SELECT * FROM monsters WHERE rare='8' AND level<='".$row['level']."' ORDER BY RAND() LIMIT 1;";
$rare7 = mysqli_query($link,$rare7) or die(mysqli_error());
$rare7 = mysqli_fetch_array($rare7);
$rare8 = "SELECT * FROM monsters WHERE rare='9' AND level<='".$row['level']."' ORDER BY RAND() LIMIT 1;";
$rare8 = mysqli_query($link,$rare8) or die(mysqli_error());
$rare8 = mysqli_fetch_array($rare8);
$rare9 = "SELECT * FROM monsters WHERE rare='10' AND level<='".$row['level']."' ORDER BY RAND() LIMIT 1;";
$rare9 = mysqli_query($link,$rare9) or die(mysqli_error());
$rare9 = mysqli_fetch_array($rare9);

Answer 1

First. You are barking the wrong tree.
Combining a number of slow queries in one won't make them fast. Overhead for running a query is NOT that important as most php users think. If query itself is fast, no matter how many times it is called (within sane numbers of course). If query is slow, no combining would help.
You have to take care for the queries themselves instead of trying to combine them. Thus, to solve your problem you have to provide a lot more info:
Define "really slows" in certain numbers. For all queries in one and for the every single query.
Provide database schema and data amounts.
Provide result of one of the queries run perpended with EXPLAIN keyword

Answer 2

You could give your monsters a random number once a day or once an hour, so
update monsters set sortorder=rand();
It might help to have an index on that key sortorder.
Then you could calculate for every read a random number in php:
$rand = mt_rand(0,1); // or however mt_rand() is called
Then you could select:
$sql23 = "SELECT * FROM monsters WHERE rare='0' AND level<='".intval($row['level'])."' ORDER BY (sortorder-$rand) DESC LIMIT 1;";
$result23 = mysqli_query($link,$sql23) or die(mysqli_error());
$battle_get23 = mysqli_fetch_array($result23);
From SQL it is easy to create a solution with only one select, but that needs a temporary table to support undisturbed random.
Use a category-table
CREATE TABLE raretype (id int(11), name varchar(255), sortkey float default 0, primary key(id));
Put your rares in there:
INSERT INTO raretype (id, name) values (0, 'battle_get23'),(1,'boss'),(2,'rare1'),...
Create a random sortorder for your read:
DROP TEMPORARY TABLE IF EXISTS tmp_rare_sort;
CREATE TEMPORARY TABLE tmp_rare_sort (raretype int(11) not null primary key, sortorder float);
INSERT INTO tmp_rare_sort SELECT id, rand() from raretype;
Read them out:
SELECT rt.name as type, m.*
FROM raretype rt
INNER JOIN tmp_rare_sort rts on rts.raretype = rt.id
LEFT JOIN monsters m on m.id =
( select id from monsters imo where imo.rare = rt.id
and imo.level <= {intval($level)}
order by abs(sortorder - rts.sortorder) desc
limit 1
)
You should read out an array as a result:
$allMonsters = array();
while($line = $rs->next()){
$allMonsters[$line['type']] = $line;
}
So that $allMonsters['boss'] gives the boss (with an additional field 'type', that should not hurt).
If you really want it as single variables, you could extract() this array.
Hope that helps!
If some syntax errors, please create a SQL-fiddle and I'll check. Just no time to create the tables myself. ;-)

Answer 3

1) take out all of your order by RAND() and limit 1
2) do randomization after query
$bossSql = "SELECT * FROM monsters WHERE rare='1' AND level<='".$row['level']."' ";
$bossRs = mysqli_query($link,$bossSql) or die(mysqli_error());
$bossArray = mysqli_fetch_array($bossRs);
//just saw you had limit in your sql, edited
//shuffle($bossArray);
$randomBosskey = array_rand($bossArray);
$randomBoss = $bossArray[$randomBossKey];
edit: thank you #flaschenpost for pointing out the potential problem, which inspired me to come up with a possibly quicker solution (under certain assumption which might not be true)
Solution 2) cache the table
From the looks of the code I think there is a high chance that you would need to do the query for monster action many times throughout the whole program lifetime.
Instead of getting a new random monster from DB everytime, will it be better to do full query:
SELECT * FROM monsters
save it in a variable and then pick the a random monster according to rarity and level from the same variable everytime you need a monster? But this method takes up unknown amount of memory depends on your table size and might be faster/slower than your original depending on how many "random monster" query you are actually using in your program. It might also depends on the "power" of your machine, assuming your DB and server are not in the same machine and the 2 machine have significant difference in processing power.