mysql PHP join - 语法问题

Question

我正在尝试加入3个表，但我的查询一直出错。 我不确定我做错了什么。 我必须做一些不正确的语法，但我不确定是什么问题。

SELECT project_timecard_tasks.DateTime,
        project_timecard_tasks.Total_Hours,
        project_timecard_tasks.User_ID,
        project_timecard_tasks.Task_ID,
        project_timecard_tasks.Project_ID,
        users.User_ID,
        users.FirstName,
        users.LastName,
        tasks.id,
        tasks.taskName

 FROM project_timecard_tasks

 JOIN project_timecard_tasks ON project_timecard_tasks.User_ID = users.User_ID 
 AND project_timecard_tasks.Task_ID = tasks.id

 WHERE project_timecard_tasks.Project_ID = '$jobNumber'

Answer 1

你的JOIN声明有点难以理解。 尝试这个：

SELECT project_timecard_tasks.DateTime,
        project_timecard_tasks.Total_Hours,
        project_timecard_tasks.User_ID,
        project_timecard_tasks.Task_ID,
        project_timecard_tasks.Project_ID,
        users.User_ID,
        users.FirstName,
        users.LastName,
        tasks.id,
        tasks.taskName

 FROM project_timecard_tasks

 JOIN users ON project_timecard_tasks.User_ID = users.User_ID 
 JOIN tasks ON project_timecard_tasks.Task_ID = tasks.id

 WHERE project_timecard_tasks.Project_ID = '$jobNumber'

Answer 2

您正在从三个表(project_timecard_tasks , users and tasks)中选择数据(project_timecard_tasks , users and tasks)但在from子句中，您只提到了一个表。 你需要提到所有的表名称，如：

 FROM project_timecard_tasks ,users, tasks

Answer 3

你加入不正确。 您需要指定要加入的表。 替换为：

JOIN users ON project_timecard_tasks.User_ID = users.User_ID 
JOIN tasks ON project_timecard_tasks.Task_ID = tasks.id

Answer 4

删除AND并在第二个连接语句中使用JOIN 。

JOIN project_timecard_tasks ON project_timecard_tasks.User_ID = users.User_ID JOIN project_timecard_tasks.Task_ID = tasks.id