如何使用having子句从DB2获取count（*）total？

Question

如何在DB2中使用group by子句获取所有返回行的总和？

例如：

Desc Ctr ---- --- 碗30 板21 勺子6 总和57

SELECT COUNT（name）为Desc，Count（*）OVER ALL GROUP BY名称

以上查询从DB2返回错误。返回所有行的SUM的正确SQL语句是什么？

谢谢， 布兰登。

Answer 1

尝试此查询，  从名称

的表组中选择名称，计数（*）

Answer 2

你的Db2平台是什么？

如果您只想要总行数，那么

select count(*)
from mytable

如果您希望按名称小计加小计，则SQL最初不支持该小计。你必须将两个结果结合起来。

select name, count(*) as cnt
from mytable
group by name
UNION ALL
select '', count(*)
from mytable

但是，更现代的版本添加了ROLLUP（和CUBE）功能......

select name, count(*) as cnt
from mytable
group by name with rollup

修改
要为name设置一个值，您可以简单地使用COALESCE()，假设除了总行外，名称不会为null。

select coalesce(name,'-Total-') as name, count(*) as cnt
from mytable
group by name with rollup

更正确的方法是使用GROUPING()功能
要么只返回旗帜

select name, count(*) as cnt, grouping(name) as IS_TOTAL
from mytable
group by name with rollup

或用它来设置文字

select case grouping(name) 
         when 1 then '-Total-'
         else name
       end as name
       , count(*) as cnt
from mytable
group by name with rollup

Inculde total

要在每一行中包含总数，您可以这样做......

with tot as (select count(*) as cnt from mytable)
select name
       , count(*) as name_cnt
       , tot.cnt as total_cnt
from mytable 
     cross join tot
group by name

请注意，这将读取mytable两次，一次为总计，另一次为详细行。但是，你所做的事情显而易见。

另一个选择就是这样

with allrows as (
   select name, count(*) as cnt, grouping(name) as IS_TOTAL
     from mytable
    group by name with rollup
)
select dtl.name, dtl.cnt, tot.cnt
from allrows dtl
     join allrows tot
        on tot.is_total = 1
where
  dtl.is_total = 0