Tables & Queries • Number lessons in a schedule

Hello world,

I'm creating a database in a music teaching environment. It creates a schedule which can be saved as an iCalendar .ics file. I already got this working, but I'm struggling in extending my SQL statement to number the lessons.

I have two tables:
- "Stammdaten", which contain all students and their weekly time which they booked (e.g. Monday, 14:00-14:45, always one student per time)
- "Kalender", containing every day of the years 2024/2025/2026 and its boolean status whether it's a school day (lessons happens only outside school holidays and bank holidays)

I get my schedule via this working SQL statement:
SELECT "Kalender"."ID", "Stammdaten"."Nachname", "Stammdaten"."Vorname", "Kalender"."Datum", "Stammdaten"."Unterrichszeitbeginn", "Stammdaten"."Unterrichtsdauer", "Stammdaten"."Fach", "Stammdaten"."Wochen", "Stammdaten"."Anzahl Stunden"
FROM "Kalender" AS "Kalender"
CROSS JOIN "Stammdaten" AS "Stammdaten"
WHERE "Kalender"."Unterrichtstag" = TRUE AND ( "Kalender"."Datum" >= "Stammdaten"."Belegungsbeginn" ) AND ( "Kalender"."Datum" <= "Stammdaten"."Belegungsende" ) AND "Stammdaten"."Unterrichtswochentag" = DAYOFWEEK( "Kalender"."Datum" )
AND ( ( "Stammdaten"."Wochen" = 'Jede' ) OR ( "Stammdaten"."Wochen" = 'Gerade' AND MOD( WEEK( "Kalender"."Datum" ), 2 ) = 0 ) OR ( "Stammdaten"."Wochen" = 'Ungerade' AND MOD( WEEK( "Kalender"."Datum" ), 2 ) = 1 ) )

This gives me a schedule showing each lesson in the future. Now I want to number the lessons: the query should add a column where the student's first lessons gets a 1, the second a 2 and so on.

I saw this thread viewtopic.php?t=99451 and tried to adapt the method, but it gives no strict incremental numbering when there are gaps in the original data.

Any hints would be much appreciated.

Harald

Statistics: Posted by HaraldS — Sat May 04, 2024 12:05 am

---