mysql PHP join - 語法問題

Question

我正在嘗試加入3個表，但我的查詢一直出錯。 我不確定我做錯了什么。 我必須做一些不正確的語法，但我不確定是什么問題。

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聲明有點難以理解。 嘗試這個：

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

您正在從三個表(project_timecard_tasks , users and tasks)中選擇數據(project_timecard_tasks , users and tasks)但在from子句中，您只提到了一個表。 你需要提到所有的表名稱，如：

 FROM project_timecard_tasks ,users, tasks

Answer 3

你加入不正確。 您需要指定要加入的表。 替換為：

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

Answer 4

刪除AND並在第二個連接語句中使用JOIN 。

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