PHP/MySQL : Using 'CONCAT' and 'AND' clause in MYSQL Query

Question

我正在尝试执行此查询:

查询 1:

$query = "SELECT a.*, b.title_wo 
          FROM `worksheet_master` AS a 
            INNER JOIN `work_order` AS b ON a.wo_number = b.wo_number 
          WHERE CONCAT (a.`wo_number` like '" . $_POST["keyword"] . "%', 
                        `title_wo` like '" . $_POST["keyword"] . "%') 
          ORDER BY a.`wo_number` DESC LIMIT 0,50";

查询 2:

$query = "SELECT a.*, b.title_wo 
          FROM `worksheet_master` AS a 
            INNER JOIN `work_order` AS b ON a.wo_number = b.wo_number 
          WHERE CONCAT (a.`wo_number` like '" . $_POST["keyword"] . "%', 
                        `title_wo` like '" . $_POST["keyword"] . "%') 
            AND a.`status` = 'NULL' 
          ORDER BY a.`wo_number` DESC 
          LIMIT 0,50";

查询 2 没有用 AND 子句给我任何结果，而查询 1 给了我结果。

谁能帮我解决这个问题？我需要整理出表中状态为空的结果，这就是为什么我在查询 2 中添加了 AND 子句，希望结果符合预期，但事实并非如此。

谢谢。

Answer 1

除非 NULL 是一个实际的字符串，否则您需要使用 IS NULL 代替。

$query = "SELECT a.*, b.title_wo 
      FROM `worksheet_master` AS a 
        INNER JOIN `work_order` AS b ON a.wo_number = b.wo_number 
      WHERE CONCAT (a.`wo_number` like '" . $_POST["keyword"] . "%', 
                    `title_wo` like '" . $_POST["keyword"] . "%') 
        AND a.`status` IS NULL 
      ORDER BY a.`wo_number` DESC 
      LIMIT 0,50";