select '类别(含EM,EN,EX)' '类别1', sum(case when(charindex('EM',tag)>0 or charindex('EN',tag)>0 or charindex('EX',tag)>0)
then id else 0 end) '总数'
,'类别(除类别1外，以E开头)' '类别2', sum(case when(charindex('EM',tag)<=0 and charindex('EN',tag)<=0 and charindex('EX',tag)<=0 
and charindex('E',tag)=2)
then id else 0 end) '总数'
,'类别(其它)' '类别3', sum(case when(charindex('E',tag)<=0) then id else 0 end) '总数'
from [tb]

------解决方案--------------------

//前面回复错了，这个为准
SQL code

--建表
create table #CarMonitor(ID int, CarID varchar(20))
--数据
insert into #CarMonitor
select 1,'苏EM' union all
select 2,'苏EM' union all
select 3,'苏EX' union all
select 4,'苏EG' union all
select 5,'京A' union all
select 6,'渝G' union all
select 7,'苏A' 
--分组统计
select case charindex('苏E',CarID) when 0 then '其他' 
   else case charindex(CarID,'苏EM,苏EN,苏EX') when 0 then '非苏EM苏EN苏EX' else '苏EM苏EN苏EX' end
      end as CarGroup, count(0) as [count] from #CarMonitor
group by case charindex('苏E',CarID) when 0 then '其他' 
   else case charindex(CarID,'苏EM,苏EN,苏EX') when 0 then '非苏EM苏EN苏EX' else '苏EM苏EN苏EX' end
      end 
--结果

CarGroup       count
-------------- -----------
非苏EM苏EN苏EX     1
其他             3
苏EM苏EN苏EX      3

(3 行受影响)

------解决方案--------------------
SQL code
--显示
SELECT * FROM table_name
ORDER BY
CASE 
    WHEN CHARINDEX(LEFT(车牌号, 3), N'苏EM,苏EN,苏EX') > 0 THEN 1  --苏EM,苏EN,苏EX为一组
    WHEN LEFT(车牌号, 2) = N'苏E' THEN 2 --不包括以上三类且以苏E开头的为一组
    ELSE 3 --其它3
END
--统计
SELECT
    车牌号类型 = 
        CASE 
            WHEN CHARINDEX(LEFT(车牌号, 3), N'苏EM,苏EN,苏EX') > 0 THEN N'苏EM|苏EN|苏EX'
            WHEN LEFT(车牌号, 2) = N'苏E' THEN N'苏E'
            ELSE N'其它'
        END,
    摄像头数量 = COUNT(1)
FROM table_name

------解决方案--------------------
因为你用的是oracle,这里是SQL SERVER版，我们的是T-SQL！
oracle里用 instr 函数代替charindex