从多个表中选择行

Question

I would like to know what the fastest way is to make the following SQL call using PHP. I am using procedural mySQLi.

$dcount = "SELECT max(id) FROM deposits";
$result = mysqli_query($conn,$dcount);
if (mysqli_num_rows($result) > 0) {
while($row = mysqli_fetch_assoc($result)) {
    $count = $row["max(id)"];
    echo $count;
    echo ",";

}
} else {
echo '0';
}

//second query
$ucount = "SELECT max(int) FROM anothertable";
$result2 = mysqli_query($conn,$ucount);
if (mysqli_num_rows($result2) > 0) {
while($row = mysqli_fetch_assoc($result)) {
    $count = $row["max(int)"];
    echo $count;
    echo ",";

}
} else {
echo '0';
}

Is there a way to make the execution faster than like this, maybe to echo the results from both queries after the first if statement?

It just seems rather long to me.

Thanks in advance.

Answer 1

SELECT max(id) as max_id, (SELECT max(int) as max_int FROM anothertable) as max_int
FROM deposits

Not tested, but something like it should work

Answer 2

SELECT d.max(id) as d_max_id, a.max(int) as a_max_int FROM deposits as d JOIN anothertable as a ON d.id = a.id;

is what you need for multiple tables

$row['d_max_id']

will give you deposits.max(id) now

You have to edit the d.id = a.id accordingly to what you want the two tables to match on

If you cant join try this:

SELECT max(id) as max_id, (SELECT max(int) FROM anothertable) as max_int FROM deposits;

Answer 3

SELECT max(id) as max_id, max(int) as max_int FROM deposits ,anothertable

Answer 4

$dcount = "
SELECT max(id) as max,'deposit' as table_name FROM deposits
UNION
SELECT max(id) as max,'another' as table_name FROM anothertable
"; 

$result = mysqli_query($conn,$dcount);
if (mysqli_num_rows($result) > 0){
  while($row = mysqli_fetch_assoc($result)){
    echo $row["table_name"].":".$row["max"]."\n";
  }
} else {
  echo '0';
}