My Data base professor uses this for the Conceptual design:
(I had to fix the words cause it wasn't in English, sorry)
Due to a few personal reasons I couldn't watch his classes, and the book I'm using won't tell me why Teacher has this double line connection with Teaches.
It is all over the place on the notes of his, and I can't study properly like this.
Does anyone care to explain it to me?
This double line says that a teacher must teach at least 1 subject. Double line shows the full participation and single line shows partial participation and it is also known as minimum cardinality.