Calculate proportion (percent) [closed]

Could you help me to calculate proportion of

Table
user_id    attendance   Date
1            1           01.01.2018
2            Null        01.01.2018
3            1           02.01.2018
4            Null        03.01.2018
5            1           03.01.2018

If user has attendance there is 1, otherwise – Null.

Need to calculate percent of attendance during 01.01.18 – 02.01.18. For instance, on 01.01.2018 there were 1 user of two (50%), on 02.01.2018 – 100%.

Tnanks!

Answer

You may try this query:

SELECT
    Date,
    100.0 * COUNT(attendance) / COUNT(*) AS perc_attendance
FROM yourTable
WHERE Date BETWEEN '2018-01-01' AND '2018-01-02'
GROUP BY
    Date;

This assumes that a given user would only appear at most once in attendance for a given date. It also assumes that your Date column is an actual date column, and not just text.

Demo