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,COUNThellip;），非

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 | 3 |

| 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 | 3 | 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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