sql - SQL Server 中的计数除以计数(*)

Question

这是我的查询:

SELECT 
    COUNT(*) AS total,
    COUNT(CASE WHEN t.id IS NULL THEN 1 END) AS nb_null,
    COUNT(CASE WHEN t.id IS NOT NULL THEN 1 END) AS nb_not_null
FROM
    table t

是否可以用别名来划分字段？ :

SELECT 
    COUNT(*) AS total,
    COUNT(CASE WHEN t.id IS NULL THEN 1 END) / total AS nb_null,
    COUNT(CASE WHEN t.id IS NOT NULL THEN 1 END) AS nb_not_null
FROM
    table t

它在 SQL Server 中对我不起作用，我想知道是否有任何方法可以做到这一点？谢谢

Answer 1

而不是

COUNT(CASE WHEN t.id is null THEN 1 END)/Count(*) 

你可以使用

AVG(CASE WHEN t.id is null THEN 1.0 ELSE 0 END)