MySQL：同一字段上具有不同WHERE的多个SELECT，结果在单独的列中

Question

I have read numerous questions regarding similar scenarios but can't quite seem to find a solution.

I have the following query to get cumulated timetrackings (stop and start are UNIX timestamps) per user per calendar week, separated by type of timetracking (project time, driving time etc.)

SELECT 
u.login as Person,
DATE_FORMAT(FROM_UNIXTIME(t.start), '%x-%v') as CalendarWeek,
t.tracking_type as TrackingType,
REPLACE(ROUND(SUM(stop-start) / 60 / 60, 2), '.', ',') AS TimeHrs
FROM ps_time_tracking t
LEFT OUTER JOIN users u ON (u.id = t.user_id)
GROUP BY Person, CalendarWeek, TrackingType
ORDER BY CalendarWeek ASC, Person ASC

The result looks like this:

| Person | CalendarWeek | TrackingType | TimeHrs | 
| ------------------------------------------------
| User A | 2018-01      | project time | 31,82   | 
| User A | 2018-01      | driving time | 4,75    | 
| User B | 2018-01      | project time | 60,17   | 
| User B | 2018-01      | driving time | 9,02    | 
| User C | 2018-01      | project time | 7,33    |

The goal would be to put the result of multiple WHEREs such as

WHERE t.tracking_type = 'project time'
WHERE t.tracking_type = 'driving time'

in different result columns:

| Person | CalendarWeek | TrackingType | ProjectTime | DrivingTime |
| --------------------------------------------------------------------
| User A | 2018-01      | project time | 31,82       | 4,75        |
| User B | 2018-01      | project time | 60,17       | 9,02        |
| User C | 2018-01      | project time | 7,33        | (null)      |

Any help would be appreciated.

Answer 1

You can use CASE to get what you need. It would look something like this:

SELECT 
u.login as Person,
DATE_FORMAT(FROM_UNIXTIME(t.start), '%x-%v') as CalendarWeek,
REPLACE(ROUND(SUM(CASE WHEN TrackingType = 'project time' THEN stop-start ELSE 0 END) / 60 / 60, 2), '.', ',') AS ProjectTime,
REPLACE(ROUND(SUM(CASE WHEN TrackingType = 'driving time' THEN stop-start ELSE 0 END) / 60 / 60, 2), '.', ',') AS DrivingTime
FROM ps_time_tracking t
LEFT OUTER JOIN users u ON (u.id = t.user_id)
GROUP BY Person, CalendarWeek
ORDER BY CalendarWeek ASC, Person ASC