MySQL的扩展SQL中有一个非常有意思的应用WITH ROLLUP，在分组的统计数据的基础上再进行相同的统计（SUM,AVG,COUNT…），非常类似于Oracle中统计函数的功能，Oracle的统计函数更多更强大。
下面演示单个司机以及所有司机的总行驶里程数和平均行驶里程数：
mysql> select name,sum(miles) as 'miles/driver' -> from driver_log group by name with rollup; +-------+--------------+ | name | miles/driver | +-------+--------------+ | Ben | 362 | | Henry | 911 | | Suzi | 893 | | NULL | 2166 | +-------+--------------+ 4 rows in set (0.00 sec) mysql> select name,avg(miles) as driver_avg -> from driver_log group by name with rollup; +-------+------------+ | name | driver_avg | +-------+------------+ | Ben | 120.6667 | | Henry | 182.2000 | | Suzi | 446.5000 | | NULL | 216.6000 | +-------+------------+ 4 rows in set (0.00 sec) mysql> select name,sum(miles) as 'miles/driver',avg(miles) as driver_avg -> from driver_log group by name with rollup; +-------+--------------+------------+ | name | miles/driver | driver_avg | +-------+--------------+------------+ | Ben | 362 | 120.6667 | | Henry | 911 | 182.2000 | | Suzi | 893 | 446.5000 | | NULL | 2166 | 216.6000 | +-------+--------------+------------+ 4 rows in set (0.00 sec)
在多个分组下WITH ROLLUP同样有效：
mysql> select srcuser,dstuser,count(*) from mail group by srcuser,dstuser; +---------+---------+----------+ | srcuser | dstuser | count(*) | +---------+---------+----------+ | barb | barb | 1 | | barb | tricia | 2 | | gene | barb | 2 | | gene | gene | 3 | | gene | tricia | 1 | | phil | barb | 1 | | phil | phil | 2 | | phil | tricia | 2 | | tricia | gene | 1 | | tricia | phil | 1 | +---------+---------+----------+ 10 rows in set (0.05 sec) mysql> select srcuser,dstuser,count(*) from mail group by srcuser,dstuser with rollup; +---------+---------+----------+ | srcuser | dstuser | count(*) | +---------+---------+----------+ | barb | barb | 1 | | barb | tricia | 2 | | barb | NULL | 3 | | gene | barb | 2 | | gene | gene | 3 | | gene | tricia | 1 | | gene | NULL | 6 | | phil | barb | 1 | | phil | phil | 2 | | phil | tricia | 2 | | phil | NULL | 5 | | tricia | gene | 1 | | tricia | phil | 1 | | tricia | NULL | 2 | | NULL | NULL | 16 | +---------+---------+----------+ 15 rows in set (0.00 sec)
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