MySQL總和不正確，並加入

Question

我正在建立一個假日系統，其中一個功能是可以購買額外的假期，你可以在一年中的幾個點上做，所以我想看到總數天假期，預訂了多少，每個用戶購買了多少。

我做一個查詢

SELECT hr_user.name AS username, 
     hr_user.user_id, 
     SUM(working_days) AS daysbooked, 
     sum(hr_buyback.days) AS daysbought 
FROM hr_leave 
inner join hr_user on hr_user.user_id = hr_leave.user_id 
left outer join hr_buyback on hr_buyback.user_id = hr_user.user_id 
where active = 'y' 
    and hr_leave.start_date between '2012-01-01' and '2012-12-31' 
    and (hr_leave.status = 'approved' OR hr_leave.status = 'pending') 
GROUP BY hr_user.name, hr_user.user_id 

現在，這是帶回導致daysbought列waaaay比我所期待的更高，這是奇怪的，因爲當我擺脫總和，只是有hr_buyback .days它顯示了所有我期望的（除了我寧願他們總結）的各個值

其次，在MySQL中，你可以做你可以在MSSQL是

left outer join hr_buyback on (select hr_buyback.user_id where buy_sell = 'buy') = hr_leave.user_id 

？

相關表定義（我認爲這是什麼意思？）：

hr_buyback

buyback_id int(11) NO PRI  auto_increment 
user_id  int(11) NO   
days  int(11) NO   
buy_sell varchar(10) NO   
status  varchar(10) NO  pending 
year  int(11) NO  

hr_user

user_id  int(11) NO PRI  auto_increment 
name  varchar(40) NO   
email  varchar(40) NO UNI  
level  int(5) YES   
manager_id int(11) NO   
team_id  int(11) YES   
active  varchar(2) NO  y 
holidays_day int(11) NO   
start_date timestamp NO  CURRENT_TIMESTAMP 
password varchar(60) NO   
division_id int(11) YES   
day_change int(5) NO  0 
priv_hours varchar(2) NO  n 
po_level int(2) YES  0 
po_signoff int(10) YES 

hr_leave

leave_id int(11) NO PRI  auto_increment 
user_id  int(11) NO   
start_date date NO   
end_date date NO   
day_type varchar(10) NO   
status  varchar(20) NO  pending 
working_days varchar(5) NO   
leave_type int(11) NO   
cancel  int(11) NO  0 
date  timestamp NO  CURRENT_TIMESTAMP 

Answer 1

這個問題可能是您將從hr_buyback獲得hr_leave中每個匹配行的每一行的一個副本。

我假設每個用戶可以有多個hr_buyback行，並且有可能有沒有hr_leave行的hr_buyback行。如果是這樣，你可能會想要這樣的事情：

SELECT hr_user.name AS username, 
    hr_user.user_id, 
    SUM(working_days) AS daysbooked, 
     (SELECT SUM(days) 
     FROM hr_buyback 
     WHERE hr_buyback.user_id = hr_user.user_id) AS daysbought 
FROM hr_user 
left join hr_leave on hr_user.user_id = hr_leave.user_id 
where active = 'y' 
and hr_leave.start_date between '2012-01-01' and '2012-12-31' 
and (hr_leave.status = 'approved' OR hr_leave.status = 'pending') 
GROUP BY hr_user.name, hr_user.user_id