优化SQL语句,该怎么处理

优化SQL语句

SQL code


  
SELECT   a.co
    ,a.c4
    ,b.c
    ,b.c9
    ,c.c9
    ,b.c4/b.c9*10000
    ,c.c4/c.c9*10000
FROM table_1 a 
RIGHT JOIN 
(SELECT co,MAX(c1) AS c1,c4,c9 FROM table_2 GROUP BY co )b
ON a.co=b.co   
LEFT JOIN table_2 c
ON b.co=c.co AND b.c1>c.c1 AND NOT EXISTS(SELECT 1 FROM table_2 WHERE co=b.co AND c1<b.c1 AND c1>c.c1)
WHERE YEAR(b.c1)=YEAR(20120331000000) AND QUARTER(b.c1)=QUARTER(20120331000000)

数据量：几十万行

SELECT co,MAX(c1) AS c1,c4,c9 FROM table_2 GROUP BY co

这个全表分组求最大耗时吗

贴一下你的 show index from a; show index from b; …

贴出执行计划show index from a; show index from b;

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