如果按连接的字符串分组，则已获得所有不同的组合。只需再添加一个字段，就可以知道每行显示sum（1）或count（1）/count（*）的次数。
编辑

SELECT concat(t1.description,t1,number, t1.date) AS UID,
CASE WHEN t2.NUM_TIMES_UID <= 1 THEN 'y' ELSE 'dummy' END AS DUMMY_VAR
FROM table t1
LEFT JOIN (
     SELECT
         concat(description,number, date) AS UID,
         SUM(1) AS NUM_TIMES_UID
     FROM table
     GROUP BY
         concat(description,number, date)
) t2 ON (concat(t1.description,t1,number, t1.date) = concat(t2.description,t2,number, t2.date))

返回分组行和该行在输入表中存在的次数的简单决策：

with items as (
select concat(description,number, date) as item
from table1
group by concat(description,number, date)
)

select item, count(item) as item_cnt
from items
group by item