postgresql 函數獲取多個字段的數字大小值

1、GREATEST(n1,n2,n3,..........) 獲取最大值

testdb=#SELECT GREATEST(3,5,1,8,33,99,34,55,67,43); 
+---------------------------------------------------------+ 
| GREATEST(3,5,1,8,33,99,34,55,67,43)                     | 
+---------------------------------------------------------+ 
| 99                                                      | 
+---------------------------------------------------------+ 
1 row in set (0.00 sec) 

2、LEAST(N1,N2,N3,N4,......) 獲取最小值

testdb=#SELECT LEAST(3,5,1,8,33,99,34,55,67,43); 
+---------------------------------------------------------+ 
| LEAST(3,5,1,8,33,99,34,55,67,43)                        | 
+---------------------------------------------------------+ 
| 1                                                       | 
+---------------------------------------------------------+ 
1 row in set (0.00 sec) 

其他更多函數參考：http://developer.51cto.com/art/201401/426252_all.htm