将2个Mysql查询合并为一个

Question

我目前正在运行两个查询以找到一个结果，我感觉可以将这两个查询合并为一个。 我已经尝试过下面的方法，但是它仍然向我显示已经从access_number表中出现的结果。

$query = "select * FROM `$table`.`access_number` WHERE `active`='1'"; 
$result = mysql_query($query,$db) or die(mysql_error());
while($row = mysql_fetch_array($result)) {
  list($dd_inuse) = mysql_fetch_row(mysql_query("SELECT `did` FROM `$table`.`customer_dd` WHERE `did`='$row[did]' AND `callerid`='$callerid' LIMIT 1",$db));
  if(!$dd_inuse) {
     $goodone = $row['did'];
     break;
   }
}

我试图像这样组合它，但并没有显示出独特的价值

select `access_number`.`did` from `access_number` 
INNER JOIN `customer_dd` 
WHERE `customer_dd`.`callerid`='$callerid' 
AND `customer_dd`.`did` !=`access_number`.`did` LIMIT 1

底线是，我正在尝试在表access_number中找到一个不存在于customer_dd

我可以为此提供任何帮助，我们将不胜感激！

Answer 1

您可以为此使用left join而not null

select 
a.access_number from access_number a
left join customer_dd c on c.did = a.did and c.callerid = '$callerid'
where c.did is null

Answer 2

您的代码：

SELECT `did` FROM `$table`.`customer_dd` 
WHERE `did`='$row[did]' AND `callerid` = '$callerid' LIMIT 1

根据您的代码，我发现您的表access_number.did = customer_dd.did 。

因此您可以尝试：

select `access_number`.`did` from `access_number` 
INNER JOIN `customer_dd` ON `customer_dd`.`did` = `access_number`.`did`
WHERE `customer_dd`.`callerid` = '$callerid' AND `access_number`.`active`='1' LIMIT 1