SQL - 加入查詢運行緩慢

Question

我想從3個不同的表中獲取數據，如下圖所示：

SELECT urs.id 
    ,urs.username 
    ,urs.b_avg_update 
    ,urs.b_set_min_avg 
    ,urs.b_set_max_avg 
    ,urs.b_min_avg 
    ,urs.b_max_avg 
    ,trs.TIME 
    ,trs.user 
    ,sum(trs.amount) 
    ,trs.type 
    ,ur.user_by 
FROM (
    SELECT DISTINCT user_by 
    FROM xeon_users_rented 
    ) AS ur 
LEFT JOIN users AS urs ON ur.user_by = urs.username 
LEFT JOIN transactions AS trs ON urs.id = trs.user 
    AND trs.type = 'Recycle' 
    AND trs.TIME >= UNIX_TIMESTAMP(CURDATE()) 
GROUP BY ur.user_by 

然而，查詢是相當緩慢運行：

Showing rows 0 - 29 (812 in total, request took 15.0095 sec) 

當運行一個EXPLAIN在上面的查詢，這是我得到：

id select_type table type possible_keys key key_len ref rows Extra 
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 1516 Using temporary; Using filesort 
1 PRIMARY urs ALL NULL NULL NULL NULL 14553 Using where; Using join buffer (flat, BNL join) 
1 PRIMARY trs ref user,type user 8 littlebu_maindb.urs.id 6 Using where 
2 DERIVED xeon_users_rented range NULL idx_user_by 62 NULL 1516 Using index for group-by 

我試圖添加INDEXES上的超速了一點東西，希望某些列：

桌上xeon_users_rented：

Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type 
xeon_users_rented 0 PRIMARY 1 id A 37897 NULL NULL  BTREE  
xeon_users_rented 0 user 1 user A 37897 NULL NULL  BTREE  
xeon_users_rented 1 user_by 1 user_by A 1579 NULL NULL  BTREE  
xeon_users_rented 1 since 1 since A 4210 NULL NULL  BTREE  
xeon_users_rented 1 expire 1 expire A 7579 NULL NULL  BTREE  
xeon_users_rented 1 clicks 1 clicks A 176 NULL NULL  BTREE  
xeon_users_rented 1 clicks_last 1 clicks_last A 5413 NULL NULL  BTREE  
xeon_users_rented 1 avg 1 avg A 3445 NULL NULL  BTREE  
xeon_users_rented 1 click_hour 1 click_hour A 46 NULL NULL  BTREE  
xeon_users_rented 1 click_minute 1 click_minute A 102 NULL NULL  BTREE  
xeon_users_rented 1 idx_click_hour 1 click_hour A 46 NULL NULL  BTREE  
xeon_users_rented 1 idx_click_minute 1 click_minute A 112 NULL NULL  BTREE  
xeon_users_rented 1 idx_id 1 id A 37897 NULL NULL  BTREE  
xeon_users_rented 1 idx_user 1 user A 37897 NULL NULL  BTREE  
xeon_users_rented 1 idx_user_by 1 user_by A 1515 NULL NULL  BTREE  
xeon_users_rented 1 idx_expire 1 expire A 6316 NULL NULL  BTREE  
xeon_users_rented 1 idx_since 1 since A 4210 NULL NULL  BTREE  
xeon_users_rented 1 idx_clicks 1 clicks A 176 NULL NULL  BTREE  
xeon_users_rented 1 idx_clicks_last 1 clicks_last A 5413 NULL NULL  BTREE  
xeon_users_rented 1 idx_avg 1 avg A 3445 NULL NULL  BTREE  

桌上users：

Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type 
users 0 PRIMARY 1 id A 14554 NULL NULL  BTREE  
users 1 idx_username 1 username A 14554 NULL NULL  BTREE  
users 1 upline 1 upline A 856 NULL NULL  BTREE  
users 1 upline 2 upline_expire A 856 NULL NULL  BTREE 

最後但並非最不重要的，transactions表：

Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type 
transactions 0 PRIMARY 1 id A 5293 NULL NULL  BTREE  
transactions 1 user 1 user A 882 NULL NULL  BTREE  
transactions 1 type 1 type A 9 NULL NULL  BTREE  
transactions 1 amount 1 amount A 378 NULL NULL  BTREE 

我看不到什麼是ca使用緩慢。總共沒有1000條記錄。 如何改進我的原始查詢和/或數據庫設計？

Answer 1

試試這個方法。我認爲users應該是JOIN的LEFT一側。但如果這不是你正在查詢的查詢，我會嘗試其他的。

SELECT urs.username 
    ,sum(trs.amount) 
FROM users AS urs 
LEFT JOIN xeon_users_rented AS ur 
     ON urs.username = ur.user_by 
LEFT JOIN transactions AS trs 
     ON urs.id = trs.user 
     AND trs.type = 'Recycle' 
     AND trs.TIME >= UNIX_TIMESTAMP(CURDATE()) 
WHERE ur.user_by IS NOT NULL 
GROUP BY ur.user_by 

Answer 2

通常，這些類型的查詢可使用相關子查詢，而不是group by在外水平運行得更快。您從transactions中拉出任意字段，因此讓我假設您只需要amount。而那username是獨一無二的。然後，你可以編寫查詢爲：

SELECT u.*, 
     (SELECT sum(trs.amount) 
     FROM transactions trs 
     WHERE u.id = trs.user AND trs.type = 'Recycle' AND 
       trs.TIME >= UNIX_TIMESTAMP(CURDATE()) 
     ) as amt 
FROM (SELECT DISTINCT user_by 
     FROM xeon_users_rented 
    ) AS xur JOIN 
    users u 
    ON xur.user_by = u.username; 

然後，users(username)和transactions(user, type, time, amount)指標是最適合這個查詢。