php - 连接名称并再次使用 concat 作为用户名？

Question

我正在尝试使用 PHP 从数据库中提取信息并进行以下查询:

$q = "SELECT CONCAT_WS(' ',FirstName,MiddleName,LastName) AS Name,
      (NewCustomerID) AS customerid,
      substring('Firstname',1,1, 'MiddleName'),
      left(MiddleName,1) AS MN,
      (LastName) AS LN
       FROM customer 
       Where FN.MN.LN = 'username'"; 
$r = mysqli_query ($dbc, $q);
$num = mysqli_num_rows($r);

当我运行它时，我得到了信息，但没有我需要的用户名:

$q = "SELECT CONCAT_WS(' ',FirstName,MiddleName,LastName) AS Name,
      (NewCustomerID) AS customerid,
      left('Firstname',1) as FN,
      left(MiddleName,1) AS MN,
      (LastName) AS LN 
            FROM customer".

只是卡住了，已经尝试了很多东西，就是无法让它工作。

Answer 1

由于FN、MN和LN是别名，您需要使用HAVING而不是哪里。

HAVING FN.MN.LN = 'username'

尽管 FN.MN.LN 是语法错误，但我假设您的意思是 CONCAT(FN,MN,LN)？

HAVING CONCAT(FN,MN,LN) = 'username'