Question

我正在寻找对以下查询的改进，感激收到任何输入

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

最简单的答案是：

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

如果在列中需要，可以使用PIVOT将Y行值移动到列中。

使用两个全表扫描CTE优化sql，现有查询

2 个答案: