php - 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。我的语法一定是做错了什么，但我不太确定哪里出了问题。

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说法有点不靠谱。试试这个：

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

您正在从三个表中选择数据，(project_timecard_tasks , users and tasks)但在from子句中您只提到 1 个表。您需要提及所有表名称，例如：

 FROM project_timecard_tasks ,users, tasks

Answer 3

你 JOIN 不正确。您需要指定要加入的表。将其替换为：

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

Answer 4

在第二个连接语句中 删除AND并使用。JOIN

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