Postgres UPDATE語句

Question

我已經從mysql移動到psql，但很難讓我的頭繞着使用多個左連接的UPDATE語句。

你會如何在Postgres中重寫？ （我正在使用postresql 9.4）

update task t 
    left join project p on t.project_id = p.id 
    left join client c on t.client_id = c.id 
    left join user u on t.user_id = u.id 
set t.project_name = p.name, 
    t.client_name = c.name, 
    t.user_name = u.name; 

任何指針都會受到歡迎。

Answer 1

在這裏你去：

WITH task_data AS (
    SELECT t.id, 
     p.name AS project_name, 
     c.name AS client_name, 
     u.name AS user_name 
    FROM task t 
     LEFT JOIN project p ON t.project_id = p.id 
     LEFT JOIN client c ON t.client_id = c.id 
     LEFT JOIN "user" u ON t.user_id = u.id 
) 
UPDATE task t 
FROM task_data d 
SET 
    project_name = d.project_name, 
    client_name = d.client_name, 
    user_name = d.user_name 
WHERE t.id = d.id 

我會很好奇，想看看是否有更有效的方式