Mysql中的if语句
1.语法
if(expr,a,b)：如果expr为真，则取a，否则取b
2.实例
mysql> select if(2>1,3,4);
+-------------+
| if(2>1,3,4) |
+-------------+
| 3 |
+-------------+
1 row in set (0.00 sec)
mysql> select if(2<1,3,4);
+-------------+
| if(2<1,3,4) |
+-------------+
| 4 |
+-------------+
1 row in set (0.00 sec)
