Question

我想知道使用PHP进行以下SQL调用的最快方法是什么。我正在使用程序化的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';
}

有没有办法让执行速度比这样快，可能是在第一个if语句之后回显两个查询的结果？

对我而言似乎相当长。

提前致谢。

Answer 1

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

未经测试，但类似的应该可以使用

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;

是您需要的多个表

$row['d_max_id']

现在会给你deposits.max（id）

您必须根据您希望两个表格匹配的内容编辑d.id = a.id

如果你不能加入试试这个：

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';
}

从多个表中选择行

4 个答案: