使用两个全表扫描CTE优化现有查询

Question

I am looking for an improvement to the below query, any input gratefully received

with cteA as (
        select name, count(1) as "A" 
        from mytable 
        where y="A"
        group by name
    ),
    cteB as (
            select name, count(1) as "B" 
            from mytable 
            where y="B"
            group by name

    )
    SELECT  cteA.name as 'name',
        cteA.A as 'count x when A',
        isnull(cteB.B as 'count x when B',0)
    FROM
    cteOne 
    LEFT OUTER JOIN 
    cteTwo
    on cteA.Name = cteB.Name
    order by 1 

Answer 1

select name, 
       sum(case when y='A' then 1 else 0 end) as [count x when A],
       sum(case when y='B' then 1 else 0 end) as [count x when B]
    from mytable
    where y in ('A','B')
    group by name
    order by name

Answer 2

The simplest answer is:

select name, y, count(*)
from mytable
where y in ('A','B')
group by name, y

You can use a PIVOT to move Y row values into columns, if you need them in columns.