如何在SQL中将行转换为计算列值

Question

我的SQL表格采用以下格式，如何转换我的表格以将CTR作为coloum？

    Date    |Type                       |count
    --------+---------------------------+------
    1-Apr   |Clicks                     |500
    1-Apr   |Impression                 |1000
    1-Apr   |distict user Clicks        |300
    1-Apr   |distict user impressions   |450
    2-Apr   |Clicks                     |520
    2-Apr   |Impression                 |1020
    2-Apr   |distict user Clicks        |320
    3-Apr   |distict user impressions   |470

我希望这会成为点击率（点击率）
例如4月1日CTR = 500/1000％= 50％ 例如4月2日CTR = 520/1020％= 42.30％

Date    |CTR    |Distict User CTR
--------+-------+------------------
1-Apr   |50%    |66.60%
2-Apr   |42.30% |68.08





SELECT 
   date , 
   CalculateCTR,      <-- How? 
   calculate DISTINCT CTR
FROM Metrics

Answer 1

修改后的透视查询应该在这里工作：

SELECT
    Date,
    100.0*MAX(CASE WHEN Type = 'Clicks' THEN count END) /
        MAX(CASE WHEN Type = 'Impressions' THEN count END) AS CTR,
    100.0*MAX(CASE WHEN Type = 'distinct user Clicks' THEN count END) /
        MAX(CASE WHEN Type = 'distinct user impressions' THEN count END) AS "Distinct User CTR"
FROM Metrics
GROUP BY Date;