Entity, Entity set (in an ER model)
Relationship, Relationship set (in an ER model)
Key constraint (in an ER model)
Participation constraint (ER)
Weak entity (ER)
ISA hierarchy (ER)
2. A music database contains information about Songs (identified by a unique
song id# and the title of the song), Bands (identified by a unique band name
and the number of members in the band), and Albums (identified by a unique
album id#, the title of the album, the number of songs on the album). Bands
sing Songs and produce Albums. Songs are parts of an Album. Draw an ER
diagram for each of the situations below:
- A Song may be part of more than one Album.
- A Song must be part of at least one Album.
- A Song appears on one and only one Album.
- Each Album must have at least one Song.
- A Band may sing more than one version of a Song, but each version must
appear on a different Album.
3. For the following relations (keys are shown with _s over the field name):
Student Class_Grade Class
___ ___ ___ ___
sname sid age gpa sid cid grade cid cdept cnum
-------------------- ------------- --------------
Ann 1 21 3.5 1 1 A- 1 CS 1621
Bob 2 19 3.4 1 2 A 2 BIOL 1011
Cal 3 20 2.6 2 1 B 3 ECE 1315