优化SQL语句

以下SQL语句执行正常，就是执行时间太长，刚接触SQL，请给优化一下

SELECT 日期,车号,SUM(a.净重) AS 煤场净重,COUNT(a.净重) AS 发煤车数, SELECT SUM(b.电厂净重)  from 日出煤统计表 b  WHERE a.日期 = b.日期 AND a.车号 = b.车号 and 电厂净重 > 0 ) as 电厂净重 （SELECT COUNT(c.电厂净重) from 日出煤统计表 c  WHERE a.日期 = c.日期 AND a.车号 = c.车号 and 电厂净重 > 0 ) as 电厂车数  from 日出煤统计表 a WHERE 净重 > 0    GROUP BY a.日期,a.车号  ORDER BY a.日期,a.车号

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把你的语句贴的规范一点。
还要断句累死人的

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as 电厂净重 后少了一个 " ,"

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那么喜欢有一句搞定？
说出你的测试语句以及结果，这样大家更容易帮你

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SELECT 日期,车号,SUM(a.净重) AS 煤场净重,COUNT(a.净重) AS 发煤车数,

(SELECT SUM(b.电厂净重)  from 日出煤统计表 b  WHERE a.日期 = b.日期 AND a.车号 = b.车号 and 电厂净重 > 0 ) as 电厂净重,

（SELECT COUNT(c.电厂净重) from 日出煤统计表 c  WHERE a.日期 = c.日期 AND a.车号 = c.车号 and 电厂净重 > 0 ) as 电厂车数 

from 日出煤统计表 a WHERE 净重 > 0   
GROUP BY a.日期,a.车号  ORDER BY a.日期,a.车号

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SELECT 日期,车号,
SUM(a.净重) AS 煤场净重,
COUNT(a.净重) AS 发煤车数,
(SELECT SUM(电厂净重)  from 日出煤统计表  WHERE a.日期 = 日期 AND a.车号 = 车号 and 电厂净重 > 0 ) as 电厂净重,
(SELECT COUNT(电厂净重) from 日出煤统计表  WHERE a.日期