oracle - 计算两个选择计数的百分比

Question

我有一个类似的查询

select count(1) from table_a where state=1;

给出 20

select count(1) from table_a where state in (1,2);

给出 25

我想要一个提取百分比 80% 的查询(将为 20*100/25)。 是否可以仅在一个查询中包含这些内容？

Answer 1

我认为无需测试以下 SQL 命令就可以做到这一点

SELECT SUM(CASE WHEN STATE = 1      THEN 1 ELSE 0 END)
      /SUM(CASE WHEN STATE IN (1,2) THEN 1 ELSE 0 END)
      as PERCENTAGE
FROM TABLE_A

或以下内容

SELECT S1 / (S1 + S2) as S1_PERCENTAGE
FROM
    (
    SELECT SUM(CASE WHEN STATE = 1 THEN 1 ELSE 0 END) as S1
          ,SUM(CASE WHEN STATE = 2 THEN 1 ELSE 0 END) as S2
    FROM TABLE_A
    )

或以下

SELECT S1 / T as S1_PERCENTAGE
FROM
    (
    SELECT SUM(CASE WHEN STATE = 1      THEN 1 ELSE 0 END) as S1
          ,SUM(CASE WHEN STATE IN (1,2) THEN 1 ELSE 0 END) as T
    FROM TABLE_A
    )

您可以选择性能或可读性!