if的用法：mysql> select if(10>9,10,9) as bigger from dual;+--------+| bigger |+--------+|     10 |+--------+left()和right()的用法：mysql> select left('abcdeft',4) a,right('abcdeft',4) b;+------+------+| a    | b    |+------+------+| abcd | deft |+------+------+with rollup的用法：select substr(tDeliverdate,1,10) riqi,sum(dSalesPrice) sale_amount from test.sale_order_detail group by riqi with rollup;+------------+-------------+| riqi       | sale_amount |+------------+-------------+| 2014-12-31 |    0.300000 || 2015-01-17 |  240.000000 || NULL       |  240.300000 |+------------+-------------+