如何使这个MySQL查询更高效？子查询/左联接

我正在寻求帮助以更快地进行查询-

SELECT DISTINCT waits.ride, 
                T2.daywait, 
                T3.timewait, 
                T4.daytimewait, 
                T5.currentwait 
FROM   waits 
       left join (SELECT Avg(waittime) AS dayWait, 
                         ride 
                  FROM   waits 
                  WHERE  dayofweek = '" . $dow . "' 
                  GROUP  BY ride) AS T2 
              ON T2.ride = waits.ride 
       left join (SELECT Avg(waittime) AS timeWait, 
                         ride 
                  FROM   waits 
                  WHERE  currenttime >= '" . $minusTime . "' 
                         AND currenttime <= '" . $plusTime . "' 
                  GROUP  BY ride) AS T3 
              ON T3.ride = waits.ride 
       left join (SELECT Avg(waittime) AS dayTimeWait, 
                         ride 
                  FROM   waits 
                  WHERE  currenttime >= '" . $minusTime . "' 
                         AND currenttime <= '" . $plusTime . "' 
                         AND dayofweek = '" . $dow . "' 
                  GROUP  BY ride) AS T4 
              ON T4.ride = waits.ride 
       left join (SELECT waittime AS currentWait, 
                         ride 
                  FROM   waits 
                  GROUP  BY ride 
                  ORDER  BY wid DESC) AS T5 
              ON T5.ride = waits.ride 
WHERE  park = '" . getPark() . "'

为了了解这个查询的应用，我使用它来填充这个链接-。如果你需要更多的信息，请告诉我

我也在寻找子查询T5的具体帮助-我想得到最近添加到每次乘坐DB waitTime的时间-有什么想法可以做到这一点吗？谢谢

只需执行一个子查询而不是四个子查询，并将表读取一次而不是四次， 您将节省3/4 75%的时间：

SELECT ride , 
   Avg( CASE WHEN dayofweek = '" . $dow . "' THEN waittime END) AS dayWait,
   Avg( CASE WHEN currenttime >= '" . $minusTime . "' 
                  AND currenttime <= '" . $plusTime . "' 
        THEN waittime END) AS dayWait,  
   Avg( CASE WHEN currenttime >= '" . $minusTime . "' 
                  AND currenttime <= '" . $plusTime . "' 
                  AND dayofweek = '" . $dow . "' 
        THEN waittime END) AS dayWait,
    waittime AS currentWait                     
FROM   waits 
GROUP  BY ride