在复杂的SQL查询中有所区别

Question

我还有另一个给你们。我一直在搜索，但我无法弄清楚这个问题的原因。

基本上，我想对user_id进行DISTINCT，这是一个自然连接的列，存在于表“user”和“leaderboard_entry”中。

这是我的原始查询，效果很好，但我想过滤掉重复项并仅显示第一个最快的用户分数。内部查询基本上抓取100个最近的行，外部查询通过升序leaderboard_entry_elapsed_time_ms对它们进行调度。

set @t1=0; select * from 
( 
   select @t1 := @t1+1 as leaderboard_entry_youngness_rank, 1-@t1/100 as 
     leaderboard_entry_youngness_based_on_expiry, 
   leaderboard_entry.*, 
   NOW()-leaderboard_entry_timestamp as leaderboard_entry_age_in_some_units , 
   TO_DAYS(NOW())-TO_DAYS(leaderboard_entry_timestamp) 
     as leaderboard_entry_age_in_days , leaderboard.leaderboard_quiz_mode , 
   leaderboard.leaderboard_load_key , 
   user.user_name 
   from leaderboard_entry 
   natural join
   leaderboard 
   natural join 
   user
   where 
   (leaderboard_load_key = 'es-en-animals-1' 
   or leaderboard_load_key = '-es-en-animals-1' ) 
   and leaderboard_quiz_mode = '0'
   order by leaderboard_entry_age_in_some_units asc , 
     leaderboard_entry_timestamp asc limit 0, 100 
) as outer_temp 
order by 
  leaderboard_entry_elapsed_time_ms asc , 
  leaderboard_entry_timestamp asc 
limit 0, 50

我尝试过以下操作，即删除“leaderboard_entry。*”，并添加DISTINCT关键字，并明确命名我需要的列：

set @t1=0; select * from 
( 
   select @t1 := @t1+1 as leaderboard_entry_youngness_rank, 1-@t1/100 as 
     leaderboard_entry_youngness_based_on_expiry, 


NOW()-leaderboard_entry_timestamp as leaderboard_entry_age_in_some_units , 
   TO_DAYS(NOW())-TO_DAYS(leaderboard_entry_timestamp) 
     as leaderboard_entry_age_in_days , leaderboard.leaderboard_quiz_mode , 
   leaderboard.leaderboard_load_key , 
   user.user_name 

distinct leaderboard_entry.user_id, 
leaderboard_entry.leaderboard_entry_id, 
leaderboard_entry.leaderboard_id, 
leaderboard_entry.leaderboard_entry_timestamp, 
leaderboard_entry.leaderboard_entry_elapsed_time_ms, 

from leaderboard_entry 
   natural join
   leaderboard 
   natural join 
   user
   where 
   (leaderboard_load_key = 'es-en-animals-1' 
   or leaderboard_load_key = '-es-en-animals-1' ) 
   and leaderboard_quiz_mode = '0'
   order by leaderboard_entry_age_in_some_units asc , 
     leaderboard_entry_timestamp asc limit 0, 100 
) as outer_temp 
order by 
  leaderboard_entry_elapsed_time_ms asc , 
  leaderboard_entry_timestamp asc 
limit 0, 50

但我得到这个错误，没有任何意义...... :(

#1064 - You have an error in your SQL syntax; 
check the manual that corresponds to your MySQL 
server version for the right syntax to use near 
'distinct leaderboard_entry.user_id, leaderboard_entry.leaderboard_entry_id, ' 
at line 12

任何帮助非常感谢！ 猪

Answer 1

上面的Scrum Meister回答