在1個查詢中選擇2個計數

試圖在一個查詢中獲取兩個不同的計數。要做到這一點，我從表中選擇，需要加入另一個。查看下面的（不工作）查詢。這是我嘗試去做的不同方式 - 不成功。在1個查詢中選擇2個計數

這是可能的，如果是的話，你可以提供幫助獲得工作查詢嗎？

SELECT 
    count(tasks_assigned.task_id) AS task_assigned_count, 
    count(tasks_created.task_id) AS task_created_count, 
FROM projects 
LEFT JOIN tasks AS tasks_assigned 
    ON tasks_assigned.project_id = projects.project_id 
    AND tasks_assigned.assigned_user_id = 1 
LEFT JOIN tasks AS tasks_created 
    ON tasks_created.project_id = projects.project_id 
    AND tasks_created.created_user_id = 1 
GROUP BY tasks_assigned.project_id, tasks_created.project_id 


SELECT 
    projects.* 
    , (SELECT count(task_id) as task_assigned_count FROM tasks as task_assigned WHERE task_assigned.project_id = projects.project_id AND assigned_user_id = 1 GROUP BY task_id) as task_assigned_count 
    , (SELECT count(task_id) as task_created_count FROM tasks as task_created WHERE task_created.project_id = projects.project_id AND assigned_user_id = 1 GROUP BY task_id) as task_assigned_count 
FROM projects

來源

2009-09-16 Louis W

SELECT 
projects.* 
, (SELECT count(*) FROM tasks WHERE project_id = projects.project_id AND assigned_user_id = 1) as task_assigned_count, 
, (SELECT count(*) FROM tasks WHERE project_id = projects.project_id AND created_user_id = 1) as task_created_count 
FROM projects

來源

2009-09-16 20:26:44

-1

SELECT (SELECT COUNT(task_id) FROM tasks_assigned) AS task_assigned_count, (SELECT COUNT(task_id) FROM tasks_created) AS task_created_count

來源

2009-09-16 20:28:15 atfergs

在子查詢擺脫分組：

SELECT 
     projects.*, 
    (SELECT count(task_id) FROM tasks 
     WHERE task_assigned.project_id = projects.project_id 
     AND assigned_user_id = 1) as task_assigned_count, 
... 
FROM projects

來源

2009-09-16 20:28:31

不是100％，如果這是你正在嘗試做的，但它看起來像你應該分組按項目ID。你可以這樣做：

SELECT projects.project_id, assigned_count.count, created_count.count 
FROM projects 
LEFT JOIN (SELECT project_id, 
        count(*) AS count, 
      FROM projects 
      INNER JOIN tasks A 
        ON tasks.project_id = projects.project_id 
      WHERE tasks.assigned_user_id = 1 
      GROUP BY projects.project_id) assigned_count 
ON assigned_count.project_id = projects.project_id 
LEFT JOIN (SELECT project_id, 
        count(*) AS count, 
      FROM projects 
      INNER JOIN tasks A 
        ON tasks.project_id = projects.project_id 
      WHERE tasks.created_user_id = 1 
      GROUP BY projects.project_id) created_count 
ON created_count.project_id = projects.project_id

或：

SELECT projects.*, 
     SUM(IF(tasks.assigned_user_id = 1,  1,0)) AS task_assigned_count, 
     SUM(IF(tasks_created.created_user_id = 1,1,0)) AS task_created_count 
FROM projects 
LEFT JOIN tasks A 
     ON tasks.project_id = projects.project_id 
GROUP BY projects.project_id

來源

2009-09-16 20:32:42

我會在兩個查詢做到這一點：

SELECT p.project_id, COUNT(a.task_id) AS task_assigned_count 
FROM projects p 
LEFT JOIN tasks AS a ON a.project_id = p.project_id 
    AND a.assigned_user_id = 1 
GROUP BY p.project_id; 

SELECT p.project_id, COUNT(c.task_id) AS task_created_count 
FROM projects p 
LEFT JOIN tasks AS c ON c.project_id = p.project_id 
    AND a.created_user_id = 1 
GROUP BY p.project_id;

否則，你所創建的tasks的兩個實例之間的笛卡爾乘積。您也可以使用DISTINCT，但這只是補償笛卡爾產品，而不是避免：

SELECT p.project_id, COUNT(DISTINCT a.task_id) AS task_assigned_count, 
    COUNT(DISTINCT c.task_id) AS task_created_count 
FROM projects p 
LEFT JOIN tasks AS a ON a.project_id = p.project_id 
    AND a.assigned_user_id = 1 
LEFT JOIN tasks AS c ON c.project_id = p.project_id 
    AND a.created_user_id = 1 
GROUP BY p.project_id;

來源

2009-09-16 20:39:32

在1個查詢中選擇2個計數

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