SELECT DISTINCT 示例

返回 CATEGORY 表中的不同类别组的列表：

select distinct catgroup from category
order by 1;

catgroup
----------
Concerts
Shows
Sports
(3 rows)

返回针对 2008 年 12 月的独特的周编号集：

select distinct week, month, year 
from date
where month='DEC' and year=2008
order by 1, 2, 3;

week | month | year
-----+-------+------
49 | DEC   | 2008
50 | DEC   | 2008
51 | DEC   | 2008
52 | DEC   | 2008
53 | DEC   | 2008
(5 rows)