mysql 中if(),left(),right(),with rollup的用法

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 |
+------------+-------------+