php - WHERE 子句错误

Question

我试图在 HTML 表格中显示数据库中的特定值。语句是这样的:(这只是一个例子)

$sql = "SELECT * FROM tbl_trainings WHERE tbl_trainings.training='Meat Processing'";

我的问题是我有这个语句(连接表):

$sql="SELECT 
tbl_info.id, 
tbl_info.firstname, 
tbl_info.middlename, 
tbl_info.lastname, 
tbl_trainings.id,
tbl_trainings.training,
tbl_trainings.info_id
  FROM tbl_info, tbl_trainings
  WHERE tbl_info.id = info_id 
  ORDER BY tbl_info.id";

我试图在这样的语句中插入 WHERE tbl_trainings.training='Meat Processing':

$sql="SELECT 
tbl_info.id, 
tbl_info.firstname, 
tbl_info.middlename, 
tbl_info.lastname, 
tbl_trainings.id,
tbl_trainings.training,
tbl_trainings.info_id
  FROM tbl_info, tbl_trainings
  WHERE tbl_info.id = info_id, tbl_trainings.training='Meat Processing'
  ORDER BY tbl_info.id";

但是我得到了错误。错误是:

警告:mysql_fetch_array() 期望参数 1 为资源，C:\wamp\www\CLphpTest\meatproc.php 中给出的 bool 值

谁能帮我改正这个问题？(对不起。还是菜鸟)

提前致谢。

Answer 1

如果您在查询中有多个条件，请添加AND/OR，例如

WHERE tbl_info.id = info_id AND
      tbl_trainings.training='Meat Processing'

另一方面，使用更新的 join 语法，

SELECT  tbl_info.id,
        tbl_info.firstname,
        tbl_info.middlename,
        tbl_info.lastname,
        tbl_trainings.id,
        tbl_trainings.training,
        tbl_trainings.info_id
FROM    tbl_info
        INNER JOIN tbl_trainings
            ON tbl_info.id = tbl_trainings.info_id
WHERE   tbl_trainings.training = 'Meat Processing'
ORDER   BY tbl_info.id